Haulover beach and Sunny Isles, Florida
by Alex Feldstein (noreply@blogger.com) at February 03, 2012 06:00 AM
Haulover beach and Sunny Isles, Florida
February 03, 2012
Alex Feldstein
Photo of the day
Haulover beach and Sunny Isles, Florida
by Alex Feldstein (noreply@blogger.com) at February 03, 2012 06:00 AM
Gravatar.com is a great and very popular Web service based way to associate an image with user accounts that are based on email addresses. It's easy to use and can provide a nice touch of personalization with very little effort to just about any Web application that uses email addresses for users. This post shows how you can use Gravatar from within your FoxPro based applications.
I recently restyled my West Wind Message Board support site and one of things that I think makes the messages look a little more interesting and personal is having an avatar - an image - associated with users. But rather than asking users to upload images and storing them on my servers, I opted to use Gravatar which is a Web based service that can be used in many applications and is supported by a large number of popular Web sites already. Ultimately it's a better choice for users who only have to sign up once to associate an email address with a Gravatar to be used on many sites.
Here's what the Gravatar image looks like on a message board message:
The Gravatar service simply returns an an image for a given email address and some other parameters that are encoded and point at the Gravatar.com site. As a developer you configure Gravatar by creating a URL and embedding that URL into an <img> control's src attribute.
Above you can see the image that is associated with my Email address. The cool thing about Gravatar - if they have a Gravatar account already - is that once users have provided an email address they don't have to do anything else to associate their gravatar image with your application. If they have a gravatar configured the image is shown. If not, a default image is shown.
If an email address is sent to Gravatar that doesn't exist you can either provide another URL to an alternate image (some sort of default that's appropriate for your app) or you can let Gravatar serve it's default icon which looks like this:
The Gravatar service works by calling a URL on their site and providing a few known parameters. An URL to retrieve an email address looks something like this:
http://www.gravatar.com/avatar/a4ec5092141a8649fe9d81527569a4c0?s=80&r=r
In an image control:
<img src="http://www.gravatar.com/avatar/a4ec5092141a8649fe9d81527569a4c0?s=80&r="
class="gravatar"
alt="Gratar Image based on email address" />
The components you need to send to get a Gravatar image are:
I've created a small reusable function that helps create Gravatar images in FoxPro. Using the function you can do:
? GravatarLink("rstrahl@west-wind.com",80) ? GravatarLink("invalid@west-wind.com",60,,"r")
Here's the code for the GravatarLink function:
************************************************************************ * GravatarLink **************************************** *** Function: Creates an image URL for a given email address *** that is registered with Gravatar.com. *** *** Gravatar is a very popular avatar service that *** requires only an email address to share a picture. *** Used on many web sites so once you sign up your *** picture will be used on many sites. *** Assume: *** Pass: lcEmail - Email Address *** lnSize - Image Size (square) 60-80 is usually good *** lcDefaultImage - Url to an image if no match is found *** for email. Empty shows Gravatar's default *** lcRating - g, pg, r, x (Default: pg) *** Return: URL to the Gravatar image ************************************************************************ FUNCTION GravatarLink(lcEmail,lnSize,lcDefaultImage, lcRating) LOCAL lcDefaultImage IF EMPTY(lnSize) lnSize = 80 ENDIF IF !EMPTY(lcEmail) lcHash = LOWER(STRCONV(HashMd5(lcEmail),15)) ELSE lcHash = "" ENDIF IF EMPTY(lcDefaultImage) *** Gravatar default image displays lcDefaultImage = "" ELSE lcDefaultImage = "&d=" + UrlEncode(lcDefaultImage) ENDIF IF EMPTY(lcRating) lcRating = "pg" ENDIF lcUrl = "http://www.gravatar.com/avatar/" + lcHash + "?" +; "s=" + TRANSFORM(lnSize) +; "&r=" + lcRating +; lcDefaultImage RETURN lcUrl * GravatarLink
The code is pretty straight forward - it basically builds up a URL as a string and adds the components provided by the parameters. The trickiest part of this is the MD5 encoding of the Email address. The MD5 hash creates a binary value which is then turned into a HexBinary string with STRCONV().
In order to encode the email address as an MD5 hash I use the following routine based on the content from the FoxPro Wiki a long while back:
************************************************************************ * wwAPI :: HashMD5 **************************************** *** Function: retrieved from the FoxWiki *** http://fox.wikis.com/wc.dll?fox~vfpmd5hashfunction *** Assume: Self standing function - not part of wwAPI class *** Pass: Data to encrypt *** Return: ************************************************************************ FUNCTION HashMD5(tcData) *** #include "c:\program files\microsoft visual foxpro 8\ffc\wincrypt.h" #DEFINE dnPROV_RSA_FULL 1 #DEFINE dnCRYPT_VERIFYCONTEXT 0xF0000000 #DEFINE dnALG_CLASS_HASH BITLSHIFT(4,13) #DEFINE dnALG_TYPE_ANY 0 #DEFINE dnALG_SID_MD5 3 #DEFINE dnCALG_MD5 BITOR(BITOR(dnALG_CLASS_HASH,dnALG_TYPE_ANY),dnALG_SID_MD5) #DEFINE dnHP_HASHVAL 0x0002 && Hash value LOCAL lnStatus, lnErr, lhProv, lhHashObject, lnDataSize, lcHashValue, lnHashSize lhProv = 0 lhHashObject = 0 lnDataSize = LEN(tcData) lcHashValue = REPLICATE(CHR(0), 16) lnHashSize = LEN(lcHashValue) DECLARE INTEGER GetLastError ; IN win32api AS GetLastError DECLARE INTEGER CryptAcquireContextA ; IN WIN32API AS CryptAcquireContext ; INTEGER @lhProvHandle, ; STRING cContainer, ; STRING cProvider, ; INTEGER nProvType, ; INTEGER nFlags * load a crypto provider lnStatus = CryptAcquireContext(@lhProv, 0, 0, dnPROV_RSA_FULL, dnCRYPT_VERIFYCONTEXT) IF lnStatus = 0 THROW GetLastError() ENDIF DECLARE INTEGER CryptCreateHash ; IN WIN32API AS CryptCreateHash ; INTEGER hProviderHandle, ; INTEGER nALG_ID, ; INTEGER hKeyhandle, ; INTEGER nFlags, ; INTEGER @hCryptHashHandle * create a hash object that uses MD5 algorithm lnStatus = CryptCreateHash(lhProv, dnCALG_MD5, 0, 0, @lhHashObject) IF lnStatus = 0 THROW GetLastError() ENDIF DECLARE INTEGER CryptHashData ; IN WIN32API AS CryptHashData ; INTEGER hHashHandle, ; STRING @cData, ; INTEGER nDataLen, ; INTEGER nFlags * add the input data to the hash object lnStatus = CryptHashData(lhHashObject, tcData, lnDataSize, 0) IF lnStatus = 0 THROW GetLastError() ENDIF DECLARE INTEGER CryptGetHashParam ; IN WIN32API AS CryptGetHashParam ; INTEGER hHashHandle, ; INTEGER nParam, ; STRING @cHashValue, ; INTEGER @nHashSize, ; INTEGER nFlags * retrieve the hash value, if caller did not provide enough storage (16 bytes for MD5) * this will fail with dnERROR_MORE_DATA and lnHashSize will contain needed storage size lnStatus = CryptGetHashParam(lhHashObject, dnHP_HASHVAL, @lcHashValue, @lnHashSize, 0) IF lnStatus = 0 THROW GetLastError() ENDIF DECLARE INTEGER CryptDestroyHash ; IN WIN32API AS CryptDestroyHash; INTEGER hKeyHandle *** free the hash object lnStatus = CryptDestroyHash(lhHashObject) IF lnStatus = 0 THROW GetLastError() ENDIF DECLARE INTEGER CryptReleaseContext ; IN WIN32API AS CryptReleaseContext ; INTEGER hProvHandle, ; INTEGER nReserved *** release the crypto provider lnStatus = CryptReleaseContext(lhProv, 0) IF lnStatus = 0 THROW GetLastError() ENDIF RETURN lcHashValue ENDFUNC * HashMD5
With this function in place it's now a snap to embed Gravatar images into HTML based applications. In a Web Connection (or any other template/script based environment that uses Fox code) you can now simply do:
<img src="<%= GravatarLink(poUser.Email,80,,"pg") %>" class="gravatar" />
And you're off to the races.
If you're a user of the West Wind Message Board I recommend you head over to Gravatar.com and hook up your Avatar image if you are interested in showing an image for any of your messages. Go ahead post a message, and see your Gravatar pop up. Once you have a Gravatar you may find that a lot of sites where you participate also already use Gravatar images so this will be useful in a lot of places beyond just the message board or your own applications.
GravatarLink() is now also part of the wwUtils library in Web Connection and the West Wind Client Tools.
Last Fall I started posting a rollup of interesting community happenings, content, samples and extensions popping up around Visual Studio LightSwitch. If you missed those rollups you can check them out here:
Looks like folks took a few well-deserved days to ramp back into the groove after the holidays (including myself). But there were still a lot of awesome things around LightSwitch this month, especially the number of submissions The Code Project had in the LightSwitch Star Contest. A lot of really interesting applications and some great case studies for LightSwitch as well as some for Azure. Check them out…
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In November The Code Project launched the “LightSwitch Star” contest. They’re looking for apps that show off the most productivity in a business as well as apps that use extensions in a unique, innovative way. Prizes are given away each month. Soon they will announce the January winners as well as the two grand prize winners of an ASUS U31SD-DH31 Laptop!
Check out all the submission we had in January and make sure to log onto Code Project and vote for your favorites. Here’s a breakdown of the 13 apps that were submitted in January (see all 34 apps that have been submitted here). There are some very creative “business apps” here – like a campaign manager for Dungeons & Dragons!
There are a lot of really interesting real-world LightSwitch production applications that were submitted. Some departmental apps, a few personal apps, some enterprise apps as well as a couple start-up companies. There are also some great case studies here for Azure, in particular:
In December I kicked off a series aimed at beginner developers just getting started with LightSwitch and was featured in the MSDN Flash Newsletter. In January we updated the Learn page of the Developer Center to feature this series and it’s been getting some great traffic!
I also released the completed source code for the sample we build in the series: Beginning LightSwitch - Address Book Sample
We also updated all the How Do I video pages to show the sequential list of videos so that you can easily get to the previous and next videos in the series. This makes it a lot easier to navigate through the over 20 videos in the correct order. Just click into any video page like this one and you will see the video navigator at the bottom of the page.
Here’s some more of the fun things the team and community released in January.
The team also released a control extension sample that you can learn from. Check out the announcement on the team blog: Many-to-Many Control Released!
Build your own extensions by visiting the LightSwitch Extensibility page on the LightSwitch Developer Center.
The Visual Studio LightSwitch Facebook Page has been increasing in activity thanks to you all. Become a fan! Have fun and interact with us on our wall. Check out the cool stories and resources.
Also here are some other places you can find the LightSwitch team:
LightSwitch MSDN Forums
LightSwitch Developer Center
LightSwitch Team Blog
LightSwitch on Twitter (@VSLightSwitch, #VisualStudio #LightSwitch)
The community has been using the hash tag #LightSwitch on twitter when posting stuff so it’s easier for me to catch it (although this is a common English word so you may end up with a few weird ones ;-)). Join the conversation! And if I missed anything please add a comment to the bottom of this post and let us know!
Enjoy!
by Alex Feldstein (noreply@blogger.com) at February 02, 2012 10:00 AM
A few days ago, ayende put up a post showing a bug that had been found in RavenDb that was causing the profiling tools to enter an infinite loop.
http://ayende.com/blog/152738/bug-hunt-what-made-this-blog-slow
This was followed by a post about how this bug had come into being and survived so long.
http://ayende.com/blog/153825/ask-ayende-what-about-the-qa-env
So confession time, that’s my bug. I contributed the early code for the profiler.
So since then I have been trying to work out how I missed it. Was I really so oblivious to what was going on while writing that code?
Second to that, how had it sat in production on ayende’s blog for 6 months or so without being noticed?
I am glad to say I have an explanation for both, which I will share now.
First some background on how the profiling actually works.
When you attach your DocumentStore to the profile, the following code is run
<script src="https://gist.github.com/1720587.js?file=RavenProfilingHandler.cs"></script>Basically we attach to the OnSessionCreated event and stuff a header into the response with the session id.
This is very important, and the key to why this bug was missed. So I will say it again, the X-RavenDb-Profiling-Id header is only added to your response if you actually open a session.
So lets look at that JavaScript again.
<script src="https://gist.github.com/1720587.js?file=ravendb-profiler-scripts.js"></script>It only calls back to the server when it gets an AJAX response that has the header set. So if you make an AJAX request to your server for data that does not come from RavenDb, the profiler will not pay any attention to that request.
The request to get the profiling results does not need a session, and in all my development it did not create a session. So it never set the header. So it never entered a loop.
So that explained to me how I had missed the bug, the way I deal with session management (creating and disposing of them only as needed) simply does not trigger the bug.
So with my conscious cleared, I moved on to the second problem. Just because I handle my session this way, clearly RacoonBlog does not, surely that bug hasn’t been there since ayende turned on the profiler for his blog.
Well let me present a commit to the RacoonBlog source from the very end of December.
https://github.com/ayende/RaccoonBlog/commit/b284efae61108af991221d948eb891e1310bc64b
In this commit, Racoon switched from creating sessions only as they are needed (my way of handling them) to creating the session in the BeginRequest event of *every* request. So even requests that don’t use the session still create one. Which obviously adds the profiling header and tells the JavaScript “this request hit RavenDb, so you should fetch it’s profiling results”.
So until that commit was pushed live RacoonBlog, like my own sites, simply did not trigger this bug, it was sitting there dormant just waiting for someone to take a different approach to session management.
So there we have it. I really don’t feel so bad about it now.
To a certain degree the JavaScript was actually correct. It noticed an AJAX request that said it had profiling information attached and it fetched that information. The fallacy in this argument though is that the JavaScript also has enough information available (the request URL) to know that it is being lied to. It should have used that information to avoid the trap that was laid for it. So it’s still a bug for all that I wish it were not.
by Chris Sainty (noreply@blogger.com) at February 02, 2012 01:18 AM
The folks at Alpha Loft announce a new meetup for Web Developers. The first meeting will feature Mark Bates talking about CoffeeScript and, no doubt, provide some insights from his upcoming book. The idea of a group focused on general web development and not a particular technology sounds like a great idea. I wish the group good luck and hope to attend future meetings.
I've been working a bit with C# custom dynamic types for several customers recently and I've seen some confusion in understanding how dynamic types are referenced. This discussion specifically centers around types that implement IDynamicObject or subclass from DynamicObject as opposed to arbitrary type casts of standard .NET types. IDynamicObject types are treated special when they are cast to the dynamic type.
Assume for a second that I've created my own implementation of a custom dynamic type called DynamicFoo which is about as simple of a dynamic class that I can think of:
public class DynamicFoo : DynamicObject { Dictionary<string, object> properties = new Dictionary<string, object>(); public string Bar { get; set; } public DateTime Entered { get; set; } public override bool TryGetMember(GetMemberBinder binder, out object result) { result = null; if (!properties.ContainsKey(binder.Name)) return false; result = properties[binder.Name]; return true; } public override bool TrySetMember(SetMemberBinder binder, object value) { properties[binder.Name] = value; return true; } }
This class has an internal dictionary member and I'm exposing this dictionary member through a dynamic by implementing DynamicObject. This implementation exposes the properties dictionary so the dictionary keys can be referenced like properties (foo.NewProperty = "Cool!"). I override TryGetMember() and TrySetMember() which are fired at runtime every time you access a 'property' on a dynamic instance of this DynamicFoo type.
I now can instantiate and use DynamicFoo in a couple of different ways:
Strong Typing
DynamicFoo fooExplicit = new DynamicFoo(); var fooVar = new DynamicFoo();
These two commands are essentially identical and use strong typing. The compiler generates identical code for both of them. The var statement is merely a compiler directive to infer the type of fooVar at compile time and so the type of fooExplicit is DynamicFoo, just like fooExplicit. This is very static - nothing dynamic about it - and it completely ignores the IDynamicObject implementation of my class above as it's never used.
Using either of these I can access the native properties:
DynamicFoo fooExplicit = new DynamicFoo();// static typing assignmentsfooVar.Bar = "Barred!"; fooExplicit.Entered = DateTime.Now;
// echo back static values Console.WriteLine(fooVar.Bar); Console.WriteLine(fooExplicit.Entered);
but I have no access whatsoever to the properties dictionary. Basically this creates a strongly typed instance of the type with access only to the strongly typed interface. You get no dynamic behavior at all. The IDynamicObject features don't kick in until you cast the type to dynamic.
If I try to access a non-existing property on fooExplicit I get a compilation error that tells me that the property doesn't exist. Again, it's clearly and utterly non-dynamic.
Dynamic
dynamic fooDynamic = new DynamicFoo();
fooDynamic on the other hand is created as a dynamic type and it's a completely different beast. I can also create a dynamic by simply casting any type to dynamic like this:
DynamicFoo fooExplicit = new DynamicFoo(); dynamic fooDynamic = fooExplicit;
Note that dynamic typically doesn't require an explicit cast as the compiler automatically performs the cast so there's no need to use as dynamic.
Dynamic functionality works at runtime and allows for the dynamic wrapper to look up and call members dynamically. A dynamic type will look for members to access or call in two places:
So rather than statically linking and calling a method or retrieving a property, the dynamic type looks up - at runtime - where the value actually comes from. It's essentially late-binding which allows runtime determination what action to take when a member is accessed at runtime *if* the member you are accessing does not exist on the object. Class members are checked first before IDynamicObject interface methods are kick in.
All of the following works with the dynamic type:
dynamic fooDynamic = new DynamicFoo(); // dynamic typing assignments fooDynamic.NewProperty = "Something new!"; fooDynamic.LastAccess = DateTime.Now; // dynamic assigning static properties fooDynamic.Bar = "dynamic barred"; fooDynamic.Entered = DateTime.Now;
// echo back dynamic values
Console.WriteLine(fooDynamic.NewProperty);
Console.WriteLine(fooDynamic.LastAccess);
Console.WriteLine(fooDynamic.Bar);
Console.WriteLine(fooDynamic.Entered);
The dynamic type can access the native class properties (Bar and Entered) and create and read new ones (NewProperty,LastAccess) all using a single type instance which is pretty cool. As you can see it's pretty easy to create an extensible type this way that can dynamically add members at runtime dynamically.
The key point here is that all three statements - explicit, var and dynamic - declare a new DynamicFoo(), but the dynamic declaration results in completely different behavior than the first two simply because the type has been cast to dynamic.
Dynamic binding means that the type loses its typical strong typing, compile time features. You can see this easily in the Visual Studio code editor. As soon as you assign a value to a dynamic you lose Intellisense and you see
which means there's no Intellisense and no compiler type checking on any members you apply to this instance.
If you're new to the dynamic type it might seem really confusing that a single type can behave differently depending on how it is cast, but that's exactly what happens when you use a type that implements IDynamicObject. Declare the type as its strong type name and you only get to access the native instance members of the type. Declare or cast it to dynamic and you get dynamic behavior which accesses native members plus it uses IDynamicObject implementation to handle any missing member definitions by running custom code.
You can easily cast objects back and forth between dynamic and the original type:
dynamic fooDynamic = new DynamicFoo(); fooDynamic.NewProperty = "New Property Value"; DynamicFoo foo = fooDynamic; foo.Bar = "Barred";
Here the code starts out with a dynamic cast and a dynamic assignment. The code then casts back the value to the DynamicFoo. Notice that when casting from dynamic to DynamicFoo and back we typically do not have to specify the cast explicitly - the compiler can induce the type so I don't need to specify as dynamic or as DynamicFoo.
This easy interchange between dynamic and the underlying type is actually super useful, because it allows you to create extensible objects that can expose non-member data stores and expose them as an object interface. You can create an object that hosts a number of strongly typed properties and then cast the object to dynamic and add additional dynamic properties to the same type at runtime. You can easily switch back and forth between the strongly typed instance to access the well-known strongly typed properties and to dynamic for the dynamic properties added at runtime.
Keep in mind that dynamic object access has quite a bit of overhead and is definitely slower than strongly typed binding, so if you're accessing the strongly typed parts of your objects you definitely want to use a strongly typed reference. Reserve dynamic for the dynamic members to optimize your code.
The real beauty of dynamic is that with very little effort you can build expandable objects or objects that expose different data stores to an object interface. I'll have more on this in my next post when I create a customized and extensible Expando object based on DynamicObject.
Astute readers (and I know who you two are!) will notice a change to a newer theme. I’ve switched over to the WordPress Twenty-Eleven base theme, with a few of my own tucks, nips and tweaks. I wanted to check out the new theme and test out the new functionality and keep up with the latest stuff.
Child themes are a piece of cake to create, and a child theme lets me override the original without messing with the original source, so updates will not erase the changes. While they are not so difficult to do manually if you are familiar with the command-line, they are even easier with the plugin One-Click Child Theme.
With the child theme in place, I was able to shorten the gap between the site description (the motto) and the header picture, just by adding CSS to the style.css in the child theme (that’s the cascading part of CSS). I added a paper-curl edge effect based on the work of Craig Buckler, published on Sitepoint.
I was disappointed that my site was not valid HTML5, according to the W3C’s validator site. Category tags used in REL links aren’t standard, so I deleted those. The Creative Commons plugins want to use Dublin Core XML namespaces, and there are issues there I’ve got to clean up. And the “generator” REL tag on the bottom of the page isn’t too standard, either. Overall, though, the pages are relatively clean of excessive markup or poorly-formed structures. Stay tuned as I tweak the last few elements into line.
by Alex Feldstein (noreply@blogger.com) at January 31, 2012 10:00 AM
Like many who were into computers “back in the day” I still maintain a nostalgic, warm and fuzzy feeling at the memory of early text based adventure games.
Back when all I knew were the PRINT and INPUT commands in QBASIC, these were the very first programs I created.
Where am I going with this?
Well over the weekend I was learning the Impress.js presentation library and thought to myself that it really was a beautiful way to display text in a web browser. Then a little light bulb went off in my head.
3 hours later, I had forked impress.js and used it’s HTML5 canvas and CSS3 animations to create an engine for a modern text adventure game.
You can see the results of that intense session of programming here http://csainty.github.com/ImpressGame
I have quite a few other ideas for what I could do with this underlying concept. If it eventually comes together as I see it, it will be beautiful.
by Chris Sainty (noreply@blogger.com) at January 31, 2012 02:39 AM
The Seacoast WordPress Developers Group will meet on February 15th at the New Hampshire Innovation Commercialization Center. I’ll talk about techniques for making backups of WordPress sites (slides and notes) and Amanda Giles will talk about custom post types. Hope to see you there!
Sign up at the Meetup site to confirm attendance.
Very often in business applications we need to validate data through another service. I’m not talking about validating the format of data entered – this is very simple to do in LightSwitch -- I’m talking about validating the meaning of the data. For instance, you may need to validate not just the format of an email address (which LightSwitch handles automatically for you) but you also want to verify that the email address is real. Another common example is physical Address validation in order to make sure that a postal address is real before you send packages to it.
In this post I’m going to show you how you can call web services when validating LightSwitch data. I’m going to use the Address Book sample and implement an Address validator that calls a service to verify the data.
In Visual Studio LightSwitch there are a few places where you can place code to validate entities. There are Property_Validate methods and there are Entity_Validate methods. Property_Validate methods run first on the client and then on the server and are good for checking the format of data entered, doing any comparisons to other properties, or manipulating the data based on conditions stored in the entity itself or its related entities. Usually you want to put your validation code here so that users get immediate feedback of any errors before the data is submitted to the server. These methods are contained on the entity classes themselves. (For more detailed information on the LightSwitch Validation Framework see: Overview of Data Validation in LightSwitch Applications)
The Entity_Validate methods only run on the server and are contained in the ApplicationDataService class. This is the perfect place to call an external validation service because it avoids having clients calling external services directly -- instead the LightSwitch middle-tier makes the call. This gives you finer control over your network traffic. Client applications may only be allowed to connect to your intranet internally but you can allow external traffic to the server managing the external connection in one place.
There are a lot of services out there for validating all sorts of data and each service has a different set of requirements. Typically I prefer REST-ful services so that you can make a simple http request (GET) and get some data back. However, you can also add service references like ASMX and WCF services as well. It’s all going to depend on the service you use so you’ll need to refer to their specific documentation.
To add a service reference to a LightSwitch application, first flip to File View in the Solution Explorer, right-click on the Server project and then select Add Service Reference…
Enter the service URL and the service proxy classes will be generated for you. You can then call these from server code you write on the ApplicationDataService just like you would in any other application that has a service reference. In the case of calling REST-ful services that return XML feeds, you can simply construct the URL to call and examine the results. Let’s see how to do that.
In this sample we have an Address table where we want to validate the physical address when the data is saved. There are a few address validator services out there to choose from that I could find, but for this example I chose to sign up for a free trial of an address validation service from ServiceObjects. They’ve got some nice, simple APIs and support REST web requests. Once you sign up they give you a License Key that you need to pass into the service.
A sample request looks like this:
http://trial.serviceobjects.com/av/AddressValidate.asmx/ValidateAddress?Address=One+Microsoft+Way&Address2=&City=Redmond&State=WA&PostalCode=98052&LicenseKey=12345
Which gives you back the result:
<?xml version="1.0" encoding="UTF-8"?> <Address xmlns="http://www.serviceobjects.com/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Address>1 Microsoft Way</Address> <City>Redmond</City> <State>WA</State> <Zip>98052-8300</Zip> <Address2/> <BarcodeDigits>980528300997</BarcodeDigits> <CarrierRoute>C012</CarrierRoute> <CongressCode>08</CongressCode> <CountyCode>033</CountyCode> <CountyName>King</CountyName> <Fragment/> </Address>
If you enter a bogus address or forget to specify the City+State or PostalCode then you will get an error result:
<?xml version="1.0" encoding="UTF-8"?> <Address xmlns="http://www.serviceobjects.com/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Error> <Desc>Please input either zip code or both city and state.</Desc> <Number>2</Number> <Location/> </Error> </Address>
So in order to interact with this service we’ll first need to add some assembly references to the Server project. Right-click on the Server project (like shown above) and select “Add Reference” and import System.Web and System.Xml.Linq.
Next, flip back to Logical View and open the Address entity in the Data Designer. Drop down the Write Code button to access the Addresses_Validate method. (You could also just open the Server\UserCode\ApplicationDataService code file if you are in File View).
First we need to import some namespaces as well as the default XML namespace that is returned in the response. (For more information on XML in Visual Basic please see: Overview of LINQ to XML in Visual Basic and articles here on my blog.) Then we can construct the URL based on the entity’s Address properties and query the result XML for either errors or the corrected address. If we find an error, we tell LightSwitch to display the validation result to the user on the screen.
Imports System.Xml.Linq Imports System.Web.HttpUtility Imports <xmlns="http://www.serviceobjects.com/"> Namespace LightSwitchApplication Public Class ApplicationDataService Private Sub Addresses_Validate(entity As Address, results As EntitySetValidationResultsBuilder) Dim isValid = False Dim errorDesc = "" 'Construct the URL to call the web service Dim url = String.Format("http://trial.serviceobjects.com/av/AddressValidate.asmx/ValidateAddress?" & "Address={0}&Address2={1}&City={2}&State={3}&PostalCode={4}&LicenseKey={5}", UrlEncode(entity.Address1), UrlEncode(entity.Address2), UrlEncode(entity.City), UrlEncode(entity.State), UrlEncode(entity.ZIP), "12345") Try 'Call the service and load the XML result
Dim addressData = XElement.Load(url) 'Check for errors first Dim err = addressData...<Error> If err.Any Then errorDesc = err.<Desc>.Value Else 'Fill in corrected address values returned from service entity.Address1 = addressData.<Address>.Value entity.Address2 = addressData.<Address2>.Value entity.City = addressData.<City>.Value entity.State = addressData.<State>.Value entity.ZIP = addressData.<Zip>.Value isValid = True End If Catch ex As Exception Trace.TraceError(ex) End Try If Not (isValid) Then results.AddEntityError("This is not a valid US address. " & errorDesc) End If End Sub End Class End Namespace
Now that I’ve got this code implemented let’s enter some addresses on our contact screen. Here I’ve entered three addresses, the first two are legal and the last one is not. Also notice that I’ve only specified partial addresses.
If I try to save this screen, an error will be returned from the service on the last row. LightSwitch won’t let us save until the address is fixed.
If I delete the bogus address and save again, you will see that the other addresses were verified and all the fields are updated with complete address information.
I hope this gives you a good idea on how to implement web service calls into the LightSwitch validation pipeline. Even though each service you use will have different requirements on how to call them and what they return, the LightSwitch validation pipeline gives you the necessary hooks to implement complex entity validation easily.
Enjoy!
by Alex Feldstein (noreply@blogger.com) at January 30, 2012 06:00 AM
by Alex Feldstein (noreply@blogger.com) at January 29, 2012 06:00 AM
by Alex Feldstein (noreply@blogger.com) at January 28, 2012 10:00 AM
public void testConnectToSMCRemoteServer() throws Exception {
SocketServer server = new SocketServer(){
public void server(Socket socket) {
try { socket.close();
} catch (IOException e) {
};
}
};
SocketService smc = new SocketService( SMCPORT, server);
boolean connection = c.connect();
assertTrue(connection);
}
SocketServer, in order to facilitate a test case of the SocketService class.
MODIFY FORM FormName, since you are able to add and override methods and properties in that form definition; Yet, (even though you could consider the form's .Name property to be the name of an Ad Hoc class) you cannot ever Sub Class that anonymous form class.
Er is weer een nieuwe DotNed podcast online. In deze podcast spreekt Maurice de Beijer met Koen Zwikstra over de recente Silverlight 5 release en hoe de toekomst er voor Silverlight ontwikkelaars uitziet. Verder vertelt hij over Silverlight Spy een runtime inspector waarmee je willekeurige Silverlight applicaties kan inspecteren. Hij kondigt ook nog even aan dat hij druk bezig is met een Spy voor Metro applicaties op Windows 8.
Links:
enjoy!
by Alex Feldstein (noreply@blogger.com) at January 27, 2012 10:00 AM
Overlayed bitmaps in FoxPro have always been a royal pain, but in order to make a UI that looks clean, getting some sort of transparency to work with FoxPro controls is pretty important. Although FoxPro supports most common image formats including GIF and PNG that support transparency, the transparency isn't supported everywhere within the product.
Specifically the FoxPro Image control supports transparency of the various transparent image formats. If you load up an image control with a GIF or PNG file, the transparency is preserved and the image displays correctly.
However, displaying transparent images on other controls that have a Picture property, unfortunately doesn't work as smoothly. Specifically, here's an example of what I've been struggling with, which is buttons with associated icons:
![ataleoftwobuttons[6]](http://www.west-wind.com/wconnect/weblog/imageContent/2012/Windows-Live-Writer/Transparent-Bitmaps-on-Buttons-and-other_C435/ataleoftwobuttons%5B6%5D.png "ataleoftwobuttons[6]")
The first button doesn't show transparency and looks terrible, while the second button properly shows transparency and appears like it should using one of the approaches mentioned below. Similar situation arises with other controls that have picture properties like OptionButton, Checkboxes. ComboBoxes and Listboxes as well, although it's less of a problem there because the background of lists tend to be white. As a matter of fact all container controls have a picture property and the same rules apply.
By default only the Image control supports transparency properly for all GDI+ image formats.
The good news is that with a bit of trickery you can get FoxPro to render transparent images. The bad news is that there are tradeoffs and extra work required to make it work properly.
GDI+ image support for non-BMP images is actually a relatively new feature in FoxPro. GDI+ support for graphics was introduced with Visual FoxPro 8. Prior to version 8 only BMP images were directly supported in the product and there are a couple of mechanisms used for handling transparency with BMPs.
The most reliable way to get transparency in FoxPro involves using BMP files and a matching BMP Mask file. The mask file basically holds black dots for each of the pixels that should display and white content for anything that should be transparent. As you might imagine creating MASK files is a pain and adds clutter to your image management - anytime the image changes the mask has to be changed too and keeping things in sync is terrible. To me this has always been a non-starter.
You can also get transparency support with only BMP images. By default BMP images display white pixels as transparent, so as long as you can easily represent your transparent content as white it's easy to do. This is not always so cut and dried however because the image 'content' may also contain white pixels. In this case you can fill the white pixels with a slightly off white color like RGB(254,254,254).
Both of these approaches are painful but they are very reliable. Once you got your image set up it always works without fail. But both approaches require that you at the very least convert them to BMP format and potentially tweak your images for transparency or by creating a mask.
There's another approach that works in most situations because of a quirk in FoxPro that I just found out about last week. FoxPro loads images as resources and you can trick FoxPro by loading images with transparency by first loading them into an Image control which as mentioned earlier does support transparency. The trick is that you have to load the image into the image control BEFORE it gets loaded into a picture property of another control. The quirk is that FoxPro caches image data once loaded from a path, so loading it into an image control first caches the transparent image which then gets loaded in subsequent loads that reference the same disk image (or compiled in image resource).
The image control has to only be loaded up and the control can then be released. The key is that this 'pre-load' has to happen BEFORE you load the same image into other controls. The image control doesn't need to stick around, so I use a small function that I only need to pass a file path to, create the Image control and set the picture property:
************************************************************************ * LoadImageResource **************************************** *** Function: Pre-load an image file so transparency is respected *** Assume: *** Pass: *** Return: ************************************************************************ FUNCTION LoadImageResource(lcFile) LOCAL loImg as Image loImg = CREATEOBJECT("Image") loImg.Picture = FULLPATH("bmps\search_small.png") ENDFUNC * LoadImageResource
When the function exits the Image control is released, but since the image was effectively loaded into the control the image is now cached inside of VFP's image cache. Now when you load an image that has been called with the function into a Picture property of another control like a button it will display GIF and PNG transparency properly.
In an application I tend to have quite a few image resources I need to load up, so centralize one place when I do all the image pre-loading during startup. I create a function that I call from the application's startup, typically right after I display a startup splash screen.
The method is simply a conglomeration of LoadImageResource() calls:
************************************************************************ * LoadImageResources **************************************** *** Function: Method is used to load up transparent images into *** UI. This method should be called on startup *** Assume: *** Pass: *** Return: ************************************************************************ FUNCTION LoadImageResources() LOCAL loImg as Image LoadImageResource("bmps\search_small.png") LoadImageResource("bmps\zipfile.gif") … ENDFUNC * LoadPictureResources
This is a simple approach that works fine and allows using PNG and GIF images with transparency on buttons and other controls.
In some instances however you can still end up with non-transparent resources. Basically FoxPro caches resources internally, but there are several ways that resources can get un-cached. Explicitly, if your code calls the CLEAR RESOURCES command anywhere, resources will get released and you'll lose any cached resources at that point. If you go back to a form with a transparent image on a control the image will display again with opaque background. Note that CLEAR RESOURCES is not affected by commands like CLEAR ALL or RELEASE ALL.
Implicitly, FoxPro can on certain occasions also unload its image resources internally when memory is really low. This should be very rare but it's possible and I have seen occasions when this does occur. But it's really rare so it's probably OK to ignore that possibility. If you're concerned about this scenario you can either have some code that calls LoadImageResources() or something like it during certain key application points that fire occasionally to explicitly force reloading of the images, or you can load resources as needed everytime a given form is fired up. This will ensure that resources are always fresh, but keep in mind that this causes some extra overhead.
I sure wish this was easier to accomplish or more obvious. For the longest time I didn't even know this hack of image pre-loading. The safest solution is to use BMP files, but it's definitely way more convenient to use Web ready files like PNGs or GIFs that support transparency both for designing the icons and re-using them across applications and platforms (Web/Desktop as I do).
Having to pre-load resources for transparent images in this fashion is a big hassle as opposed just loading up image resources directly. And worse it's an ugly hack that's impossible to discover on your own. I found a vague reference to this on a message board message somewhere so it's even hard to search for. Hopefully this blog entry will help clarfiy the subject a little better, even if it's just for me to remember in the future.
What really sucks about this problem is the fact that it DOES works with preloaded image resources. This seems to suggest that transparency actually works on controls but there's a small implementation detail in Visual FoxPro that prevents this from working all the time. It seems this would have been such a minor thing for the Fox team to fix and get working out of the box if the resources to do so had been there. But alas, we're stuck with a few minor and undiscoverable hacks. I take a hack over it not working at all which was what I thought until a week ago.
Thanks to Cesar Chalom, Joel Leach, Dragan Nedeljkovich for providing some ideas for this post and Mike Lewis for providing the inspiration to look further into this and getting me to a working solution in Html Help Builder.
Overlayed bitmaps in FoxPro have always been a royal pain, but in order to make a UI that looks clean, getting some sort of transparency to work with FoxPro controls is pretty important. Although FoxPro supports most common image formats including GIF and PNG that support transparency, the transparency isn't supported everywhere within the product.
Specifically the FoxPro Image control supports transparency of the various transparent image formats. If you load up an image control with a GIF or PNG file, the transparency is preserved and the image displays correctly.
However, displaying transparent images on other controls that have a Picture property, unfortunately doesn't work as smoothly. Specifically, here's an example of what I've been struggling with, which is buttons with associated icons:
The first button doesn't show transparency and looks terrible, while the second button properly shows transparency and appears like it should using one of the approaches mentioned below. Similar situation arises with other controls that have picture properties like OptionButton, Checkboxes. ComboBoxes and Listboxes as well, although it's less of a problem there because the background of lists tend to be white. As a matter of fact all container controls have a picture property and the same rules apply.
By default only the Image control supports transparency properly for all GDI+ image formats.
The good news is that with a bit of trickery you can get FoxPro to render transparent images. The bad news is that there are tradeoffs and extra work required to make it work properly.
GDI+ image support for non-BMP images is actually a relatively new feature in FoxPro. GDI+ support for graphics was introduced with Visual FoxPro 8. Prior to version 8 only BMP images were directly supported in the product and there are a couple of mechanisms used for handling transparency with BMPs.
The most reliable way to get transparency in FoxPro involves using BMP files and a matching BMP Mask file. The mask file basically holds black dots for each of the pixels that should display and white content for anything that should be transparent. As you might imagine creating MASK files is a pain and adds clutter to your image management - anytime the image changes the mask has to be changed too and keeping things in sync is terrible. To me this has always been a non-starter.
You can also get transparency support with only BMP images. By default BMP images display white pixels as transparent, so as long as you can easily represent your transparent content as white it's easy to do. This is not always so cut and dried however because the image 'content' may also contain white pixels. In this case you can fill the white pixels with a slightly off white color like RGB(254,254,254).
Both of these approaches are painful but they are very reliable. Once you got your image set up it always works without fail. But both approaches require that you at the very least convert them to BMP format and potentially tweak your images for transparency or by creating a mask.
There's another approach that works in most situations because of a quirk in FoxPro that I just found out about last week. FoxPro loads images as resources and you can trick FoxPro by loading images with transparency by first loading them into an Image control which as mentioned earlier does support transparency. The trick is that you have to load the image into the image control BEFORE it gets loaded into a picture property of another control. The quirk is that FoxPro caches image data once loaded from a path, so loading it into an image control first caches the transparent image which then gets loaded in subsequent loads that reference the same disk image (or compiled in image resource).
The image control has to only be loaded up and the control can then be released. The key is that this 'pre-load' has to happen BEFORE you load the same image into other controls. The image control doesn't need to stick around, so I use a small function that I only need to pass a file path to, create the Image control and set the picture property:
************************************************************************ * LoadImageResource **************************************** *** Function: Pre-load an image file so transparency is respected *** Assume: *** Pass: *** Return: ************************************************************************ FUNCTION LoadImageResource(lcFile) LOCAL loImg as Image loImg = CREATEOBJECT("Image") loImg.Picture = FULLPATH("bmps\search_small.png") ENDFUNC * LoadImageResource
When the function exits the Image control is released, but since the image was effectively loaded into the control the image is now cached inside of VFP's image cache. Now when you load an image that has been called with the function into a Picture property of another control like a button it will display GIF and PNG transparency properly.
In an application I tend to have quite a few image resources I need to load up, so centralize one place when I do all the image pre-loading during startup. I create a function that I call from the application's startup, typically right after I display a startup splash screen.
The method is simply a conglomeration of LoadImageResource() calls:
************************************************************************ * LoadImageResources **************************************** *** Function: Method is used to load up transparent images into *** UI. This method should be called on startup *** Assume: *** Pass: *** Return: ************************************************************************ FUNCTION LoadImageResources() LOCAL loImg as Image LoadImageResource("bmps\search_small.png") LoadImageResource("bmps\zipfile.gif") … ENDFUNC * LoadPictureResources
This is a simple approach that works fine and allows using PNG and GIF images with transparency on buttons and other controls.
In some instances however you can still end up with non-transparent resources. Basically FoxPro caches resources internally, but there are several ways that resources can get un-cached. Explicitly, if your code calls the CLEAR RESOURCES command anywhere, resources will get released and you'll lose any cached resources at that point. If you go back to a form with a transparent image on a control the image will display again with opaque background. Note that CLEAR RESOURCES is not affected by commands like CLEAR ALL or RELEASE ALL.
Implicitly, FoxPro can on certain occasions also unload its image resources internally when memory is really low. This should be very rare but it's possible and I have seen occasions when this does occur. But it's really rare so it's probably OK to ignore that possibility. If you're concerned about this scenario you can either have some code that calls LoadImageResources() or something like it during certain key application points that fire occasionally to explicitly force reloading of the images, or you can load resources as needed everytime a given form is fired up. This will ensure that resources are always fresh, but keep in mind that this causes some extra overhead.
I sure wish this was easier to accomplish or more obvious. For the longest time I didn't even know this hack of image pre-loading. The safest solution is to use BMP files, but it's definitely way more convenient to use Web ready files like PNGs or GIFs that support transparency both for designing the icons and re-using them across applications and platforms (Web/Desktop as I do).
Having to pre-load resources for transparent images in this fashion is a big hassle as opposed just loading up image resources directly. And worse it's an ugly hack that's impossible to discover on your own. I found a vague reference to this on a message board message somewhere so it's even hard to search for. Hopefully this blog entry will help clarfiy the subject a little better, even if it's just for me to remember in the future.
What really sucks about this problem is the fact that it DOES works with preloaded image resources. This seems to suggest that transparency actually works on controls but there's a small implementation detail in Visual FoxPro that prevents this from working all the time. It seems this would have been such a minor thing for the Fox team to fix and get working out of the box if the resources to do so had been there. But alas, we're stuck with a few minor and undiscoverable hacks. I take a hack over it not working at all which was what I thought until a week ago.
Thanks to Cesar Chalom, Joel Leach, Dragan Nedeljkovich for providing some ideas for this post and Mike Lewis for providing the inspiration to look further into this and getting me to a working solution in Html Help Builder.
Some folks have been asking for this so I just released the completed Address Book sample that you build step-by-step in the Beginning LightSwitch Article Series.
.png)
Download the Address Book SampleAre you completely new to LightSwitch and software development? Read this entry-level article series to get started with the most important concepts you need to build any LightSwitch application.
Visit the LightSwitch Developer Center to download LightSwitch and get started learning.
.png)
Download Visual Studio LightSwitch
.png)
Watch the instructional LightSwitch "How Do I?" videos
.png)
Ask questions in the LightSwitch forums
Enjoy!
by Alex Feldstein (noreply@blogger.com) at January 26, 2012 10:00 AM
Been playing with jAlbum again. Check this album for more pics.
It’s about 8 months since my first contribution to an open source project. It was followed up minutes later by one to reverse all the accidental formatting changes I made. Damn you Visual Studio!
I am happy to say that it was not an isolated contribution though.
Now I am by no means a prolific contributor and my spare time is more often spent tinkering with my own ideas and projects rather than working hard on open source. However, there has been a steady enough flow of pull requests and projects to keep me satisfied that I am at least involved.
RavenDb and Nancy are where most of my focus has been. Two great examples of modern C# open source development.
In my own right there have been RavenDb plugins for Glimpse and MvcMiniProfiler.
Straying from C# there is even a start being made on a Node.js client for RavenDb. Getting started with Node has been an absolute blast, and my first serious attempt at adding a new language to my skill set since C#. Sure I’ve dabbled with jQuery heavy javascript in the past to add a little life to a web page, but truly learning the object model and scoping rules of javascript is a different beast entirely.
Most recently, as in last week, I have been pitching in at Code52, a new idea for this year which tackles a new project every week. It has been very .NET focussed so far, but that is simply a product of the founding core of developers having .NET backgrounds. At the end of the day, the people who are in the chat room at the start of each project are the ones who decide the technology stack. I hope to get them doing a Node project at some point this year.
The project from last week was IdeaStrike a UserVoice inspired (clone?) site that you can simply deploy to AppHarbor and manage yourself to track ideas and gather feedback about your product. You can see it in action at http://ideastrike.apphb.com/.
It uses Nancy and Entity Framework. I wouldn’t call it a best practice example of either at the moment, it is tough to refactor a project that goes from start to finish in a week. It is however a good example of a non-trivial application, with (some) tests, in Nancy.
Even though the week is up, the project does not stop there. People are always welcome to fork, change, commit and send through a pull request.
A full list of previous projects, that will update over the year, can be found at http://code52.org/projects.html.
This week the focus is a cross-platform multiplayer game. Much further out of my comfort zone, but a great chance to learn some XNA, and eventually Android and iOS when those clients are added.
Now this is a fairly reflective post, not my usual style, but the point is really just to spread the word. There are lots of interesting projects around, big and small, in almost any language you care to use. Just pick one and jump in.
by Chris Sainty (noreply@blogger.com) at January 25, 2012 11:07 PM
Paul Irish started the idea of an HTML5 Boilerplate, a template to start the basic web application with the common features, and addressed problems, of HTML5 and CSS3.
Behold Op
en Source Power: “my” base CSS for next project, is v 2.0, with 209 well-reviewed commits from 49 practitioners.
There’s a dream team of coders and well-tested code I couldn’t imagine assembling in real life.
Now, there’s a web site that will generate and optionally customize the base templates for you: http://www.initializr.com/
by Alex Feldstein (noreply@blogger.com) at January 25, 2012 10:00 AM
Using Entity Framework Code First together with SqlServerCe is a great way to work with small databases in ASP.NET MVC applications. I have several web applications running on shared hosting sites where SqlServerCe is the database engine under the hood. Deploying is also quite easy. I typically use the build in Publish Web option which works great over FTP.
When using SqlServerCe you have to make sure you add the deployable dependencies. Forgetting those results in pretty clear error messages.
However once that is done I always run into another issue. When a page actually tries to use SqlServerCe I will see a security exception:
System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
The solution is simple enough. Go to whatever security portal your provider is using, mine is using Plesk, and make sure the user that is actually running the web site has the required read/write privileges to work with the Bin folder.
Enjoy!
by Alex Feldstein (noreply@blogger.com) at January 24, 2012 10:00 AM
| Current name | Previous names |
|---|---|
| Christof Wollenhaupt | Christof Lange |
| Cathy Knight | Cathy Pountney |
| Toni Feltman | Toni Taylor
Toni Taylor-Feltman |
Set of VFP string functions implemented in T-SQL by Brad Schulz| TYPE | VFP | T-SQL |
|---|---|---|
| AutoIncrement field last value | GETAUTOINCVALUE | SCOPE_IDENTITY() / OUTPUT clause in SQL Server 2005 and up. [NEW] See also: Find the IDENTITY value of the last inserted row (discussion on @@IDENTITY, SCOPE_IDENTITY() and IDENT_CURRENT(), and which one to use). See also http://blog.sqlauthority.com/2007/03/25/sql-server-identity-vs-scope_identity-vs-ident_current-retrieve-last-inserted-identity-of-record/ |
| Inline Condition | IIF(condition,true value, false value) | CASE WHEN condition THEN true value ELSE false value END |
| BETWEEN | BETWEEN(field,low value, high value) | field BETWEEN lowvalue AND highvalue. Better yet, just use the SQL BETWEEN instead of the VFP between() in all cases when writing SQL (VFP or NOT) |
| True/False | .T. / .F. | No logical data type 1=1/1=2 |
| Check something is NULL | ISNULL(checked_value) | IS [NOT] NULL this syntax worked in VFP also |
| Get non NULL value from two expressions | NVL(checked_value,value_if_expression_is_null) | ISNULL(checked_value,value_if_expression_is_null) Also COALESCE ( expression [ ,...n ] ) - returns the first nonnull expression among its arguments. |
| String comparison | = for partial, == for exact. LIKE is supported since at least VFP v7 -- Mike Yearwood | LIKE |
| Empty Dates | {} | Not supported. Use NULL instead |
| Checking for an empty string | EMPTY(fieldname). EMPTY() has never been Rushmore optimizable. Try fieldname = space(len(fieldname)) or UPPER(fieldname) = SPACE(LEN(fieldname)) especially if you have an index on UPPER(fieldname). -- Mike Yearwood | LEN(fieldname) = 0 |
| Current Date and Time | DateTime() | GetDate() or DATEADD(ms,-DATEPART(ms,GETDATE()),GETDATE()) because GetDate() return datetime with ms |
| Current Date | Date() | Date data type doesn't exist In SQL Server 2008 there are new DATE and TIME types |
| Add/Subtract from a date | Use arithmetic operators Date() + 1 or Date() - 1 | DATEADD(day,1,Getdate()) or to substract use a negative integer You can directly add/subtract dates from getdate(): select getdate() - 31, getdate() + 30 Regarding the last comment - you can not do this with Dates in SQL Server 2008 see Compatibility Clash in 2008 |
| Compare two dates | logic symbols<,>,= | DATEDIFF ( datepart , startdate , enddate ) |
| Date constant or literal | curly braces and an uproot example: {^2006/01/31} | Several format with single quotes example: 'April 15, 1998' '15 April, 1998' '980415' '04/15/98' |
| Get the integer portion of a number | INT() | CAST(somenumber AS int) |
| Convert date to sortable string | DTOS(date-value) | CONVERT(char(8), date-value, 112) |
| Replace text in a string | STRTRAN() | REPLACE() |
| [NEW] Trim string | LTRIM(), TRIM() or RTRIM(), ALLTRIM() | LTRIM(), RTRIM(), LTRIM(RTRIM()) |
| Number of occurrences of a character in a string | OCCURS() | How many occurrences in a string |
| Pad a string with space | PADR(somestring,numchars) PADL(somestring,numchars) | CAST(somestring AS char(numchars)) REPLICATE(SPACE(1), numchars - DATALENGTH(somestring )) + somestring , PADR(),PADL(),PADC() |
| Convert an integer to fixed length zero padded | PADL(intval,numchars, '0') | REPLICATE('0', numchars - DATALENGTH( CAST(intval AS varchar(numchars)) )) + CAST(intval AS varchar(numchars)) |
| Find text in a string | AT() $ | CHARINDEX(), PATINDEX() LIKE |
| Return a string within in a string | SUBSTR() | SUBSTRING() |
| A string length | LEN() | DATALENGTH() LEN() - doesn't count trailing spaces |
| Checking a list of values | [NOT] INLIST(valuelookingfor, testval1, testval2, testval3) IN / NOT IN works in VFP also | valuelookingfor [NOT] IN (testval1, testval2, testval3) If value is in another table, then INNER JOIN / LEFT JOIN with IS NULL may be a better alternative |
| Deleting all records | ZAP [IN nWorkArea | cTableAlias] | TRUNCATE TABLE tablename |
| Determine last query rowcount | _TALLY | @@ROWCOUNT |
| Replaces each character in a character expression that matches a character in a second character expression with the corresponding character in a third character expression. | CHRTRAN() | |
| Removes all characters from a string except those specified. | [NEW] CHRTRAN(cString, CHRTRAN(cString, cFilter, "), ") | Igor's Nikiforov UDF StrFilter |
| Counts the words in a string. | GETWORDCOUNT() | Igor's Nikiforov UDF GetWordCount |
| Returns a specified word from a string. | GETWORDNUM() | Igor's Nikiforov UDF GetWordNum |
There’s a neat new front end to the caniuse.com HTML 5 reference at http://html5please.us/ – it’s hard to keep up on all the browser versions and who does what.
One of the problems with HTML5, or development at the cutting edge of the web, has always the need to support a large number of different browsers. Depending on who you ask the numbers will vary slightly but is usually boils down to Internet Explorer being the biggest and Chrome and FireFox each taking quite a big chunk of the stats and the remainder of the browsers filling up the gaps.
So that means that any public facing website should at the very least support the three major browsers, not to bad right?
Turns out that live isn’t quite as good as that. With Chrome and FireFox most users are at or close to the last revision of the browser but with Internet Explorer this isn’t the case. In fact as the chart below shows the majority is still using IE8 with IE9 only accounting for a little over a third of all IE users.
So what the big difference?
There are 2 reasons.
First of all IE9 is only available on Windows Vista and Windows 7 and it turns out there is still a substantial number of people using Windows XP. For all those users Internet Explorer 8 is the latest version of the browser they can use. And that is not going to change when Internet Explorer 10 ships. However that number of XP users isn’t that large.
The second and more important reason is that Microsoft doesn’t automatically update Internet Explorer when a newer version is available. You can download it if you want to but if you don’t explicitly do so nothing happens. And by contrast all recent versions of FireFox and Chrome are self updating, so whenever a new version is available it is downloaded without any explicit user action. The benefit is that with both Chrome and FireFox a web developer wanting to do cutting edge HTML5 stuff can be pretty confident that a user has an up to date browser. Well except with Internet explorer that is 
Microsoft has seen the update light
Fortunately that won’t be a problem much longer. Recently Microsoft has announced that it will start auto updating Internet Explorer using Windows Update. So no longer are we dependent on users going in and manually doing an update, instead if they don’t take any action they will be automatically upgraded to the last possible version of IE. This means that we should soon see at leas two thirds of all IE users use IE9, and more important for HTML5 developers, a more compliant browser with a much faster JavaScript engine.
Of course IE9 still isn’t perfect because it supports less HTML5 features than both Chrome and FireFox but the fact that the JavaScript engine is much faster makes it much easier when using polyfills to insert missing pieces. And the fast JavaScript engine and more compliant rendering engine is great news for all web developers 
And the this update will mean that adoption of IE10 will be a lot faster when it ships later this year.
The auto update doesn’t start worldwide right away. At first it will start in Australia and Brazil only. But when that is done they plan on doing so in more countries around the world.
A big step forwards for Microsoft and a huge step forward for HTML5 developers all over the world 
Enjoy!
by Alex Feldstein (noreply@blogger.com) at January 23, 2012 10:00 AM
| TYPE | VFP | T-SQL |
|---|---|---|
| AutoIncrement field last value | GETAUTOINCVALUE | SCOPE_IDENTITY() / OUTPUT clause in SQL Server 2005 and up See also http://blog.sqlauthority.com/2007/03/25/sql-server-identity-vs-scope_identity-vs-ident_current-retrieve-last-inserted-identity-of-record/ |
| Inline Condition | IIF(condition,true value, false value) | CASE WHEN condition THEN true value ELSE false value END |
| BETWEEN | BETWEEN(field,low value, high value) | field BETWEEN lowvalue AND highvalue. Better yet, just use the SQL BETWEEN instead of the VFP between() in all cases when writing SQL (VFP or NOT) |
| True/False | .T. / .F. | No logical data type 1=1/1=2 |
| Check something is NULL | ISNULL(checked_value) | IS [NOT] NULL this syntax worked in VFP also |
| Get non NULL value from two expressions | NVL(checked_value,value_if_expression_is_null) | ISNULL(checked_value,value_if_expression_is_null) Also COALESCE ( expression [ ,...n ] ) - returns the first nonnull expression among its arguments. |
| String comparison | = for partial, == for exact. LIKE is supported since at least VFP v7 -- Mike Yearwood | LIKE |
| Empty Dates | {} | Not supported. Use NULL instead |
| <new> Checking for an empty string | EMPTY(fieldname). EMPTY() has never been Rushmore optimizable. Try fieldname = space(len(fieldname)) or UPPER(fieldname) = SPACE(LEN(fieldname)) especially if you have an index on UPPER(fieldname). -- Mike Yearwood | LEN(fieldname) = 0 |
| Current Date and Time | DateTime() | GetDate() or DATEADD(ms,-DATEPART(ms,GETDATE()),GETDATE()) because GetDate() return datetime with ms |
| Current Date | Date() | Date data type doesn't exist <new> In SQL Server 2008 there are new DATE and TIME types |
| Add/Subtract from a date | Use arithmetic operators Date() + 1 or Date() - 1 | DATEADD(day,1,Getdate()) or to substract use a negative integer You can directly add/subtract dates from getdate(): select getdate() - 31, getdate() + 30 Regarding the last comment - you can not do this with Dates in SQL Server 2008 see Compatibility Clash in 2008 |
| Compare two dates | logic symbols<,>,= | DATEDIFF ( datepart , startdate , enddate ) |
| Date constant or literal | curly braces and an uproot example: {^2006/01/31} | Several format with single quotes example: 'April 15, 1998' '15 April, 1998' '980415' '04/15/98' |
| <new> Get the integer portion of a number | INT() | CAST(somenumber AS int) |
| Convert date to sortable string | DTOS(date-value) | CONVERT(char(8), date-value, 112) |
| Replace text in a string | STRTRAN() | REPLACE() |
| Trim string | TRIM(), RTRIM() ALLTRIM() | RTRIM() LTRIM(RTRIM()) |
| <new> Number of occurrences of a character in a string | OCCURS() | How many occurrences in a string |
| Pad a string with space | PADR(somestring,numchars) PADL(somestring,numchars) | CAST(somestring AS char(numchars)) REPLICATE(SPACE(1), numchars - DATALENGTH(somestring )) + somestring , PADR(),PADL(),PADC() |
| Convert an integer to fixed length zero padded | PADL(intval,numchars, '0') | REPLICATE('0', numchars - DATALENGTH( CAST(intval AS varchar(numchars)) )) + CAST(intval AS varchar(numchars)) |
| Find text in a string | AT() $ | CHARINDEX(), PATINDEX() LIKE |
| <new> Return a string within in a string | SUBSTR() | SUBSTRING() |
| A string length | LEN() | DATALENGTH() LEN() - doesn't count trailing spaces |
| Checking a list of values | [NOT] INLIST(valuelookingfor, testval1, testval2, testval3) IN / NOT IN works in VFP also | valuelookingfor [NOT] IN (testval1, testval2, testval3) <new> If value is in another table, then INNER JOIN / LEFT JOIN with IS NULL may be a better alternative |
| Deleting all records | ZAP [IN nWorkArea | cTableAlias] | TRUNCATE TABLE tablename |
| Determine last query rowcount | _TALLY | @@ROWCOUNT |
| Replaces each character in a character expression that matches a character in a second character expression with the corresponding character in a third character expression. | CHRTRAN() | |
| Removes all characters from a string except those specified. | STRFILTER() | Handy String functions |
| Counts the words in a string. | GETWORDCOUNT() | Handy String functions |
| Returns a specified word from a string. | GETWORDNUM() | Handy String functions |
Things are starting to feel "normal" again here (whatever that means, and it doesn't mean much). I'm going to post something M would probably have enjoyed, or at least argued with me about -- which amounted to enjoyment for both of us.
I'm trying to use a new-ish feature in SQL Server -- Policy Based Management -- and figuring out the best way to create my own policy condition. Conditions are a building block of policies, and SQL Server comes with a whole bunch in-the-box.
If you don't see the default set of conditions, you haven't installed the policies that reference conditions. When you Import Policies from the shipping set (check BOL for the location of these XML files in your SQL Server installation), they drag along the conditions they need.
But what if the conditions you need aren't included? That's when the fun begins. As usual in SQL Server, there are probably at least 5 ways to express the conditions you'll want to check; what's the best way?
I'll walk through creating a condition here, and show you how I made a design decision when face with such a choice.
The example policy and its underlying conditions that I'll use in this walkthrough aren't available in-the-box, as far as I could tell. That's probably because this example checks for a problem that's incredibly stupid. Nobody should ever have it.
On the other hand, that doesn't mean this is not a real (and realistic) example. This problem does happen in my environment and maybe it happens in yours, too.
So here we go.
Yeah, it's sad but true: there are several people who:
Specifically, they sometimes deploy the object without setting the right database context first.
They usually figure it out right away when they try to reference the newly-deployed (or newly-updated) object, and it doesn't do what they expect. They quickly re-deploy.
Meanwhile, some of these people have, or used to have, a default database of "Master". After they've re-deployed, they're often blissfully ignorant of why the first version didn't show up in the correct database as expected, or just don't care. The mistakenly-deployed version is still sitting around in the system database, which just bugs me.
I decided that I wanted to do a periodic check of all my environments of any code in any of the system databases that shouldn't be there.
Using a Central Management Server, this is easy to do with a SQL statement that hits every server in a managed group. The statement to check the master database might look like this:
select @@SERVERNAME as ServerName, count(*) as NonMSCount
from master.sys.objects
where is_ms_shipped = 0
If you want to check all three system databases in one statement, you might write the following:
select @@SERVERNAME as ServerName, sum(NonMSCount) from
(select count(*) as NonMSCount from master.sys.objects
where is_ms_shipped = 0
union all
select count(*) from msdb.sys.objects
where is_ms_shipped = 0 and name not like 'sys%'
union all
select count(*) from model.sys.objects
where is_ms_shipped = 0) xx
... don't get too hung up on the actual SQL statements; I'm sure you can do it better. The highlighted item, for example, is just my lazy way of accounting for the fact that msdb.dbo.sysdtslog90 is installed on demand with SSIS therefore is_ms_shipped is not 0 -- at least on my local box. Your mileage may vary.
The point here is that I am summing three numbers (a count of non-MS-provided database objects in each of the system databases). If the total is not zero, I'll borrow from the immortal Ricky Ricardo and say "Lisa's got some 'splaining to do." I'm not going to take any automated action, I'm not going to yell at anybody in a grumpy email alert, there may be a good reason for that user code... I just want to review it. OK?
Why bother turning this easy code into a Policy? Why not just issue the statement(s) you see above, manually?
It comes down to the advantage of declaratively, explicitly installing the policy into SQL Server (in this case, via a Central Management Server). I could run the script every once in a while, and it would have the same result.
I could even declare the intent in a Sharepoint page, where everybody would know the plan, assuming they read the Sharepoint page... which they will not.
But if I install the policy, with a suitable name, it will carry more weight with the relevant personnel.
Plus, it's actually easier to retrieve and run.
I could do a similar thing by creating a DTSX package and running that at intervals, of course. It would also be very visible to the same personnel. I love SSIS. But, in this case, a DTSX would be overkill, harder to maintain, and not nearly as cool, besides.
Policies are a declarative way of exposing, instituting, evaluating, and managing best practices. Unlike SSIS, they don't do anything else, they're tuned for this.
So how do we get started?
First, you create the conditions you want to check, and then you create the policy that references these conditions.
We have already designed the "conditions" we want to check in our policy, by writing the SQL statements above.
In typical SQL Server Management Studio style, drill down through the Object Explorer in the Management node, where you'll find a Policy Management area. Opening this, you find Policies, Conditions, and Facets. Right-click on the Conditions node to start creating a new Condition, and give it a suitable name:
I've used the facet "Server" here, because it seems most appropriate to me. Think of this basically as the scope of the command I'm going to run. I need to run it once per server, not once per database on the server, right? Hold that thought for a moment.
Note: there are lots of other facets, such as Data File, Application Role, Server Settings, and they all seem disparate, but the same thought process is going to hold true. If you think of the facet as a collection of something over which you're going to run something like a For each..., you'll probably pick the right facet.
You'll know if you've picked a really wrong facet for your purpose, in the next step, if the nested dialog doesn't give you any attributes that make sense for the scope you had in mind. For example, if I pick the facet Remote Service Binding, I'm going to get an attribute called @CertificateUser and another one called @IsAnonymous. Keep holding that thought.
On the second panel of this dialog, you'll give the condition a good description, I hope. Take a look at the MS-created ones; they're complete with recommendations, URLs for further reference, etc.
In my screenshot, you can see this isn't a complete condition yet, because I haven't created an expression that represents what this condition is supposed to, well, express. That's where our "several ways to do something" comes in. We know what we want to say; how are we going to say it?
Do what the dialog suggests; "Click here to add a clause". What the heck are you supposed to do here ? The "Field" dropdown supplies attributes that belong to a Server (our chosen facet), but how do they relate to the SQL we're using for this condition?
They don't! And that's okay. Press the ellipsis to the right of the Field dropdown to get to the following nested dialog:
... as you can see, we have the use of a function to execute the SQL statement(s) of our choice.
What should the condition be?
You have at least the following choices:
Add(
Add ( ExecuteSql( 'Numeric' , 'select COUNT(*) from model.sys.objects
where is_ms_shipped = 0'),
ExecuteSql ('Numeric' , 'select COUNT(*) from master.sys.objects
where is_ms_shipped = 0')
),
ExecuteSql('Numeric' , 'select COUNT(*) from msdb.sys.objects
where is_ms_shipped = 0
and name not like '''sys%'')
)
No matter which of the three you choose, once you have a fully-posable condition, you can reference it in a policy.
With any of these methods, once you've created (and saved) your condition, creating the policy based on it is simple:
Right-click on the Policies node in Object Explorer, to create a New Policy similarly to how you created a New Condition. For our purposes, you just have to choose the condition you created earlier as the correct one to reference for the new policy; nothing else is required and at this level, which method you used to create your conditionn is completely irrelevant:
So, what difference will it make which method you used to create the condition?
The first attempt I made, simply transferring my compound SQL statement into a single clause, was the easiest one for me to do. I just told the policy to do exactly what I'd been doing manually in SQL Management Studio. If I stopped there, however, I wouldn't really be taking advantage of what policies have to offer in terms of process and management.
The second attempt I made, adding the nested Add() functions, doesn't really provide any particular advantage. Working through that version (with lots of sidebars and messing about) simply satisfied me with regards to how flexible and useful the condition syntax would be, to move things out of ExecuteSQL when appropriate.
Why did I care about the available condition expression syntax? SQL is easiest for us SQL jocks, but ExecuteSQL conditions can't be put in policies that need to execute on a schedule, rather than On Demand. Not a big deal in this case, but worth learning for later.
Both of these methods have the same weakness: if the policy check fails, you're not going to know which system database has the errant object. You're not even going to see anything much in the Evaluation Results dialog, because your Condition field expression is pretty convoluted.
By contrast, when you run a policy based on the third method, all you have to do is look at your results and you can see right away exactly which clause failed:
Here, we learn that making the condition building blocks more granular is a better practice. We'll keep that in mind for the future.
One reason you might not want multiple clauses, for some conditions, is that, if one of the clauses can't have an "automatic fix/apply" result, that will take away this type of resolution for all the clauses. In our example scenario, there's no "automatic fix/apply" for any of our clauses, so there isn't any problem.
Is "more granular" always better?
You have additional choices, if you want, and if you change the the facet against which you apply the condition:
As you can see, you can create a new condition to indicate the correct target databases on the server you're evaluating. In this case, your new condition to filter the targets could use either the @Name of the database or the @IsSystemObject attribute of the database.
In this case, I didn't feel that was a correct resolution. Remember: I had a slight exception in the check that I wanted to make for the msdb database; I couldn't execute exactly the same code against each system database.
If you want to go all-out-granular, you could even choose to create different conditions, and execute a different policy, for facets aimed at the individual object types: one for Stored Procedure, one for User-Defined Types, etc. But, in my example scenario, declaring a separate policy for each object type would dilute the message my policy is trying to send: it doesn't matter what the object type is, I don't want the individuals in question to even think there is such a distinction. Object-level is really the wrong scope for my purposes. Not to mention, it would be a PITA for me to evaluate all these policies separately!
I hope this gives you some ideas about how you might use conditions you design yourself, and how to make some of the design decisions you'll face.
If you're already using policies, you've probably already figured all this out and don't even realize it can be troublesome. But I can tell you, when starting out, I looked at available guidance and didn't see what I was looking for.
Using a SQL-based condition is not ideal, and may not take full advantage of what policies have to offer; you can't use them to enforce any policy, not just this one, automatically. As you can see from the "Apply to targets" mechanism I've just discussed, and because the facets have lots of attributes and the policy condition expression syntax is quite rich, there may definitely be a way to define my condition/rule without using ExecuteSQL at all.
Maybe I'll check that out some other time -- although I suspect it would run slower, and, in this case, I don't care about the restriction anyway.
Meanwhile, I would like Central Management Server queries and, possibly, policies attached to them, to be more flexible in their results. What do I mean by that? I think I'll post a separate example showing you, after thinking it through a little more.
Double-meanwhile, you'll doubtless let me know what you think.
by Alex Feldstein (noreply@blogger.com) at January 22, 2012 10:01 AM
The whitepapers on my web site will help you get started. http://www.craigberntson.com -- Craig BerntsonTwo VFP-related links:
Rick Strahl: How to work around Visual FoxPro's 16 Megabyte String Limit.
ActiveVFP updated at CodePlex.
| Current name | Previous names |
|---|---|
| Christof Wollenhaupt | Christof Lange |
by Alex Feldstein (noreply@blogger.com) at January 21, 2012 10:00 AM
I had a reader ask a question this week on how to use Visual Studio LightSwitch to open different Edit Detail screens based on the “type” of record. This is a very common thing to do especially for data models that use table inheritance (or sub-tables). For instance say we are building an application for a pet store to manage their inventory of animals. We need to collect shared properties of all the animals in an Animal table but we also want to set up table inheritance to Fish, Cat and Dog tables which collect specific properties of those types of animals. When a user selects an animal on a search screen, we need to display a screen that lets them work with the correct data from the specific table. LightSwitch provides a “Show as Link” on labels which automatically opens up the default details screen for that entity, but in our case we could have multiple screens. There are also a few techniques you need to know when dealing with these types of relationships in LightSwitch, particularly around the insert pipeline. In this post I will show you how you can achieve this functionality.
First let’s start by creating a simple inheritance data model for the pet store. We will build an Animal table that collects general properties of any animal in the store. Then we will build Cat, Dog and Fish tables to collect specific properties of those types of animals. The relationship between the Animal table and the others will be a ‘one to zero or one’ relationship.
For this example, the Animal table has two required properties, Name and Type. Type is a Choice List with the static values “Cat”, “Dog”, “Fish” to correspond to the type of record the animal is. We will use this to drive what records are inserted into which specific table as well as use it to determine which screens to display.
Next, create the Cat, Dog and Fish tables to collect properties specific to these types of animals.
Finally, set up the relationships from Animal to these tables as a “one to zero or one” relationship with a delete behavior of “Cascade Delete”.
Our data model now looks like this.
Next we’ll need to enter new animals into the system. Create a New Data Screen and select Animal as the screen data. When you do this, LightSwitch will include all the one-to-one related tables as fields on the screen. However, we only want to require the user to enter the general Animal properties on this screen. Once they save, we will direct them to the correct Cat, Dog or Fish detail screen. So first delete all the items in the content tree of the Screen Designer except for Name and Type.
Next, create an Edit Details Screen and select the Animal screen data again. Name the screen CatDetail and uncheck “Use as Default Details Screen”.
Again you will see that LightSwitch reads these special relationships and adds all the fields from all four tables to the screen. We will need to make some changes. First, change the “Type” from an Auto Complete box to a Label. Once the user has entered the type of animal on the New Data screen, it cannot be changed. Next, delete all the fields related to Dog and Fish from the screen.
Repeat the same process to create the DogDetail and FishDetail screens, removing the fields from the screen that do not belong.
Finally, add a Search Data Screen and select the Animal as the screen data again. Select the “Name” content item and in the properties window uncheck “Show as Link”.
Instead of using the built-in “Show as Link” functionality, we need to create our own command. We can put commands anywhere on the screen and we can show them as buttons or links. (For more information see: “I Command You!” - LightSwitch Screen Commands Tips & Tricks) For instance we could put an edit button on the screen command bar, the grid command bar, or even in the row itself. Let’s add a command into the row itself.
Right-click on the Data Grid Row Command Bar in the content tree and select “Add Button…”. Create a new method called “Edit”.
We want to show the command as a link instead of a button so select the button in the content tree and change it to a link.
Now we need to write some code to pull this all together. Right-click on the button we just created and select “Edit Execute Code” to open the code editor. Here we will check what type of animal we have to open the corresponding screen.
Private Sub Edit_Execute() If Me.Animals.SelectedItem IsNot Nothing Then Select Case Me.Animals.SelectedItem.Type Case "Cat" Me.Application.ShowCatDetail(Me.Animals.SelectedItem.Id) Case "Dog" Me.Application.ShowDogDetail(Me.Animals.SelectedItem.Id) Case "Fish" Me.Application.ShowFishDetail(Me.Animals.SelectedItem.Id) End Select End If End Sub
Next we need to write similar code on the New Data screen so that it opens the correct detail screen after the user saves a new animal record. Open the CreateNewAnimal screen and in the upper right drop down the “Write Code” button and select the CreateNewAnimal_Saved method. First comment out the call to ShowDefaultScreen and then write code to determine which screen we need to show instead:
Private Sub CreateNewAnimal_Saved() Me.Close(False) 'Application.Current.ShowDefaultScreen(Me.AnimalProperty) Select Case Me.AnimalProperty.Type Case "Cat" Me.Application.ShowCatDetail(Me.AnimalProperty.Id) Case "Dog" Me.Application.ShowDogDetail(Me.AnimalProperty.Id) Case "Fish" Me.Application.ShowFishDetail(Me.AnimalProperty.Id) End Select End Sub
Finally, we need to implement a business rule on Animal in the save pipeline. This rule is important so that a new record is added to the correct table based on the animal’s type. That way after the user saves the CreateNewAnimal screen, a record will be written to the correct table and the detail screen will open and allow the user to edit the specific fields in the Cat, Dog or Fish table. Double-click on Animals in the Solution Explorer under the Data Sources/ApplicationData node to open the Data Designer. Drop down the Write Code button and select the Animals_Inserting method and write this code:
Private Sub Animals_Inserting(entity As Animal) Select Case entity.Type Case "Cat" If entity.Cat Is Nothing Then entity.Cat = New Cat() End If Case "Dog" If entity.Dog Is Nothing Then entity.Dog = New Dog() End If Case "Fish" If entity.Fish Is Nothing Then entity.Fish = New Fish() End If End Select End Sub
Enter new animals on the Create New Animal screen and when you click Save, the correct detail screen will open allowing you to enter more specific details based on the type of animal.
On our search screen, we can click the Edit link on any of the rows and it will open to the correct details screen as well.
I hope this post answered the reader’s question on how to open different detail screens depending on the record’s type. All it takes is implementing your own command. I also touched on one to one relationships and how to set up basic table inheritance. I encourage you to experiment more with this type of relationship. They come in particularly handy when you need to extend external data sources with additional properties or when you need to set up inheritance hierarchies. The trick is to get a record inserted into the right table when you insert the master / parent record. I’ll expand on a couple other techniques in a future post.
Enjoy!
Thanks everyone for joining in with the DevelopMentor webinar I did last night on Getting Started with WCF and Rest.
If you want to take another look at the slides or samples you can download them using the links below:
For more info about the WCF Web API you can check the WCF CodePlex site.
Enjoy!
Can't decide if these are palms or Dr. Suess' truffula trees
L pointed out the curious frost that formed on the windows overnight in the sub-zero weather. I can’t decide if Jack Frost was dreaming of palm trees or Dr. Suess’ truffula trees.
West Wind Technologies has released version 4.66 of West Wind Html Help Builder. Help Builder produces documentation for Html Help (CHM), Web ready HTML and Word/PDF format for end user applications as well as developer documentation for FoxPro, .NET, Sql Server, Web Services and other environments. Version 4.66 adds many small user interface enhancements to the IDE and a host of new backup and project export features to Zip files. There are also a number of improvement for .NET imports including support for Code Contracts and multiple example code snippets. There are also a host of small UI improvements and a few bug fixes. Help Builder is available as shareware and registered users can download and re-install the latest version.If you take a look at the Visual FoxPro documentation and the System Limits you find that FoxPro's string length limit is somewhere around ~16mb. The following is from the FoxPro Documentation:
Maximum # of characters per character string or memory variable: 16,777,184
Now 16mb seems like a lot of data, but in certain environments like Web applications it's not uncommon to send or receive data larger than 16 megs. In fact, last week I got a message from a user of our Client Tools lamenting the fact that the HTTP Upload functionality does not allow for uploads larger than 16 megs. One of his applications is trying to occasionally upload rather huge files to a server using our wwHttp class. At the time I did not have a good solution for him due to the 16meg limit.
The FoxPro documentation actually is not quite accurate! You can actually get strings much larger than 16megs into FoxPro. For example you can load up a huge file like the Office 2010 download from MSDN like this:
lcFile = FILETOSTR("e:\downloads\en_office_professional_plus_2010_x86_515486.exe") ? LEN(lcFile)
The size of this string: 681,876,016 bytes or 681megs! Ok that's a little extreme :-) but to my surprise that worked just fine; you can load up a really huge string in VFP if you need to. But when you get over 16megs the behavior of strings changes and you can't do all the things you normally do with strings.
Other operations do not work for example, the following which creates an 18meg string fails:
lcString = REPLICATE("1234567890",1800000)
with "String is too long to fit".
However the following which creates a 25 meg string does work:
lcString = REPLICATE("1234567890",1500000) lcString = lcString + REPLICATE("1234567890",1000000) ? LEN(lcString) && 25,000,000
The following is almost identical except it copies the longer string to another string which does not work:
lcString = REPLICATE("1234567890",1500000) lcNewString = lcString + REPLICATE("1234567890",1000000)
And that my friends is the real sticking point with large strings. You can create them, but once they get bigger than 16megs you can no longer assign them to a new variable. That might sound easy to avoid but it's actually tough to do. If you pass string to methods it's very likely that they are actually copied into temporary variables or added to another variable in a simulated buffer, and that is typically where large strings fail.
So what can we learn from this:
Doesn't Work:
Works:
There are some limitations but knowing that if you work with a single string instance that can grow large is actually good news. What this means is that if you're careful with how you use strings in FoxPro you can fairly easily get around the 16 meg string limit.
This actually worked well for me in the wwHttp class and the POST issue for larger than 16meg files but not string. Internally wwHttp uses a cPostBuffer property to hold the POST data. The failure was occuring in the send code which would copy the string to a temporary string and get the size, then pass that to the WinInet APIs. The fix for this was fairly easy: Rather than creating the temporary variables (which were redundant anyway) I simply used the class property directly throughout the code without any hand off and voila, now wwHttp supports POSTs for greater than 16 megs.
The code I use is kinda ugly because it's doing lots of string concatenation to build up the Post buffer. Something along these lines like this excerpt from wwHttp::AddPostKey:
************************************************************************ * wwHTTP :: AddPostKey ********************************* *** Function: Adds POST variables to the HTTP request *** Assume: depends on nHTTPPostMode setting *** Pass: *** Return: ************************************************************************ FUNCTION AddPostKey(tcKey, tcValue, llFileName) LOCAL lcOldAlias tcKey=IIF(VARTYPE(tcKey)="C",tcKey,"") tcValue=IIF(VARTYPE(tcValue)="C",tcValue,"") IF tcKey="RESET" OR PCOUNT() = 0 THIS.cPostBuffer = "" RETURN ENDIF *** If we post a raw buffer swap parms IF PCOUNT() < 2 tcValue = tcKey tcKey = "" ENDIF IF !EMPTY(tcKey) DO CASE *** Url Encoded CASE THIS.nhttppostmode = 1 THIS.cPostBuffer = this.cPostBuffer + IIF(!EMPTY(this.cPostBuffer),"&","") + ; tcKey +"="+ URLEncode(tcValue) *** Multi-part formvars and file CASE this.nHttpPostMode = 2 *** Check for File Flag - HTTP File Upload - Second parm is filename IF llFileName THIS.cPostBuffer = THIS.cPostBuffer + "--" + MULTIPART_BOUNDARY + CRLF + ; [Content-Disposition: form-data; name="]+tcKey+["; filename="] + JUSTFNAME(tcValue) + ["]+CRLF+CRLF this.cPostBuffer = this.cPostBuffer + FILETOSTR(FULLPATH(tcValue)) this.cPostBuffer = this.cPostBuffer + CRLF ELSE this.cPostBuffer = this.cPostBuffer +"--" + MULTIPART_BOUNDARY + CRLF + ; [Content-Disposition: form-data; name="]+tcKey+["]+CRLF+CRLF this.cPostBuffer = this.cPostBuffer + tcValue ENDIF ENDCASE ELSE *** If there's no Key post the raw buffer this.cPostBuffer = this.cPostBuffer +tcValue ENDIF ENDFUNC
AddPostKey can accept either a string value or a filename to load from. The file loading works by accepting the filename and then directly loading the file from within the function:
this.cPostBuffer = this.cPostBuffer + FILETOSTR(FULLPATH(tcValue))
This works fine because the file is directly loaded up into the buffer with no intermediate string variable.
You cannot however pass a string that is greater than 16 megs into this function because the code that adds the key basically does this with the tcValue parameter:
this.cPostBuffer = this.cPostBuffer + tcValue
which is assigning the larger than 16 meg string (tcValue in this case) to another variable and as discussed earlier that fails with "String too long to fit". Using a string to buffer your output to build up a larger string, there's no workaround for adding a larger than 16 meg string to another variable or buffer using variables. So my code now works with files loaded from disk, but not string parameters
Good but not good enough!
Based on the earlier examples I showed we know that we can easily load up massive content from a file. Thus FILETOSTR() offers an easy way to serve large files. Knowing that it's possible to build stream like class that allows you to accumulate string content in a file and then later retrieve it. To do this I created a wwFileStream class. Using the class looks like this:
*** Load library DO wwapi *** Create 20 meg string lcString = REPLICATE("1234567890",1500000) lcString = lcString + REPLICATE("1234567890",500000) *** Create a stream loStream = CREATEOBJECT("wwFileStream") *** Write the 20meg string loStream.Write(lcString) *** Add some more string data loStream.WriteLine("...added content") *** Now write a 16meg+ to the buffer as well loStream.WriteFile("e:\downloads\ActiveReports3_5100158.zip") *** Works lcLongString = loStream.ToString() *** 55+ megs ? loStream.nLength ? LEN(lcLongString) *** Clear the file (auto when released) loStream.Dispose()
Using this mechanism you can build up very large strings from files or strings regardless of what the size of the string is.
Internally wwFileStream opens a low level file and tracks the handle. Each Write() operation does an FWRITE() to disk and the handle is released when the class goes out of scope.
The class implementation is pretty straight forward:
************************************************************* DEFINE CLASS wwFileStream AS Custom ************************************************************* *: Author: Rick Strahl *: (c) West Wind Technologies, 2012 *:Contact: http://www.west-wind.com *:Created: 01/04/2012 ************************************************************* nHandle = 0 cFileName = "" nLength = 0 ************************************************************************ * Init **************************************** FUNCTION Init() this.cFileName = SYS(2023) + "\" + SYS(2015) + ".txt" this.nHandle = FCREATE(this.cFileName) this.nLength = 0 ENDFUNC * Init ************************************************************************ * Destroy **************************************** FUNCTION Destroy() this.Dispose() ENDFUNC * Destroy ************************************************************************ * Dispose **************************************** FUNCTION Dispose() IF THIS.nHandle > 0 TRY FCLOSE(this.nHandle) DELETE FILE (this.cFileName) CATCH ENDTRY ENDIF this.nLength = 0 ENDFUNC * Destroy ************************************************************************ * Write **************************************** FUNCTION Write(lcContent) THIS.nLength = THIS.nLength + LEN(lcContent) FWRITE(this.nHandle,lcContent) ENDFUNC * Write ************************************************************************ * WriteLine **************************************** FUNCTION WriteLine(lcContent) this.Write(lcContent) this.Write(CHR(13) + CHR(10)) ENDFUNC * WriteLine ************************************************************************ * WriteFile **************************************** FUNCTION WriteFile(lcFileName) lcFileName = FULLPATH(lcFileName) this.Write(FILETOSTR( lcFileName )) ENDFUNC * WriteFile ************************************************************************ * ToString() **************************************** FUNCTION ToString() LOCAL lcOutput FCLOSE(this.nHandle) lcOutput = FILETOSTR(this.cFileName) *** Reopen the file this.nHandle = FOPEN(this.cFileName,1) FSEEK(this.nHandle,0,2) RETURN lcOutput ENDFUNC * ToString() ************************************************************************ * Clear **************************************** FUNCTION Clear() THIS.Dispose() THIS.Init() ENDFUNC * Clear ENDDEFINE *EOC wwFileStream
The code is fairly self explanatory. The class creates a file in the temp folder and saves the handle. Any write operation then uses the file handle to FWRITE() either a string or the output from FILETOSTR(). ToString() can be called to retrieve the file, which closes the file, reads it then reopens it and points to the end. When the class is released the handle is closed and the handle released.
Using this class makes it easy to create large strings and hold onto them. The additional advantage is that memory usage is kept low as strings are loaded up only briefly and then immediately written to file and can be released. So if you're dealing with very large strings a class like this is actually highly recommended. In fact Web Connection uses this same approach for file based application output.
While the FileStream class works, it does have some overhead compared to memory based operation especially when you're dealing with small amounts of data. In the wwHttp class for example, I would not want to create a new wwFileStream for each POST operation. 99% of POST ops are going to be light weight, so it makes sense to only use the wwFileStream class selectively.
In order to do this I also created a wwMemoryStream class which has the same interface as wwFileStream and which uses a simple string property on the class to hold data. Since the classes have the same interface they are interchangable in use which makes them easily swappable.
The code for wwMemoryStream looks like this:
************************************************************* DEFINE CLASS wwMemoryStream AS Custom ************************************************************* *: Author: Rick Strahl *: (c) West Wind Technologies, 2012 *:Contact: http://www.west-wind.com *:Created: 01/05/2012 ************************************************************* cOutput = "" nLength = 0 ************************************************************************ * Destroy **************************************** FUNCTION Destroy() THIS.Dispose() ENDFUNC * Destroy ************************************************************************ * Dispose **************************************** FUNCTION Dispose() this.cOutput = "" this.nLength = 0 ENDFUNC * Dispose ************************************************************************ * Clear **************************************** FUNCTION Clear() this.cOutput = "" this.nLength = 0 ENDFUNC * Clear ************************************************************************ * Write **************************************** FUNCTION Write(lcContent) this.nLength = this.nLength + LEN(lcContent) this.cOutput = this.cOutput + lcContent ENDFUNC * Write ************************************************************************ * WriteLine **************************************** FUNCTION WriteLine(lcContent) this.Write(lcContent) this.Write(CRLF) ENDFUNC * WriteLine ************************************************************************ * WriteFile **************************************** FUNCTION WriteFile(lcFileName) this.Write(FILETOSTR( FULLPATH(lcFileName) )) ENDFUNC * WriteFile ************************************************************************ * ToString() **************************************** FUNCTION ToString() RETURN this.cOutput ENDFUNC * ToString() ENDDEFINE *EOC wwMemoryStreamIt's now a cinch to create my class depending on the need.
In wwHttp I use wwMemoryStream by default since it addresses the 99% scenario. I added two properties to wwHttp: oPostStream and cPostStreamClass. The class is set to wwMemoryStream which is the default and can be overridden. Then internally when the time comes to create an instance of the stream class I use:
IF VARTYPE(this.oPostStream) != "O" this.oPostStream = CREATEOBJECT(this.cPostStreamClass) ENDIF
This way the user can easily chose which of the streams to use simply by specifying:
loHttp.cPostStreamClass = "wwFileStream"
What's also nice about this approach is that the mechanism becomes extensible. If you want to store POST vars in another storage format you can simply create another subclass that implements the same methods and now can store your post variables in an INI file or in structured storage etc. Unlikely scenario for POST data, but very useful for other potential data storage scenarios.
BTW, the wwFileStream class is also a fairly useful generic file output tool. If you ever need to write output to files it provides a real easy OO way to do so, cleaning up after itself when you close it. I've used classes like (wwResponseFile) for years in various applications that need to create file output. It's very useful in many situations.
Even though Visual FoxPro has a 16 meg string limit, you now have some tools in your arsenal to work around this limit and work with larger strings. While you can work with larger strings, keep in mind that once you go past 16 megs you can't assign that string to anything else. It also gets much harder (and slower) to string manipulation on that string once you're beyond VFP's legal limit.
Still it's nice to know that the limit is not a final one and there are ways to work around it.
--Paul McNett, Earthling
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