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RIA & Ajax: Article

Silverlight and Astoria - First Impressions

In short, an Astoria service is a WCF service that sits on top of an Entity Model that allows you to hit services with URLs

Kevin Hoffman's Blog

As you know, Silverlight is a new RIA enabling technology from Microsoft. Slightly less publicized but no less impactful is another technology from Microsoft - Astoria. Astoria is a tool that combines the power of the ADO.NET Entity Framework with the new enhanced power of RESTful POX services using WCF. In short, an Astoria service is a WCF service that sits on top of an Entity Model that allows you to hit services with URLs that look something like this:

http://server/service.svc/Customers/Orders[TotalAmount>25.50]

This will return a bunch of XML corresponding to all of the customer orders that have a total amount greater than $25.50. The syntax / query format of the URL itself is one of the things that makes the Astoria service so unbelievably powerful. You can sort, filter, limit, and paginate all from the URL itself, making client implementations incredibly easy, and incredibly well-suited to lightweight GUI frameworks like AJAX or Silverlight.

To keep it short and simple, here's what I did (using the "Orcas" beta 1 w/Silverlight toolkit installed AND Astoria toolkit installed):

  1. Create a new ASP.NET Web Application. Warning!! - I couldn't get this to work unless I created this using File -> New -> Project -> ASP.NET Web Application. For some reason, the current beta of Silverlight/Astoria have compatibility issues with File -> New -> Website.
  2. Right-click the ASP.NET Web Application and choose "Add new item", then pick "ADO.NET Entity Data Model". In my case, I generated it from an existing database that had a couple of sample tables, including a Ledger table containing transactions.
  3. Right-click the ASP.NET project and choose "Add new item". Pick "Web Data Service". Make sure it has the word data in it, otherwise you're going to get a vanilla Web Service and not an Astoria Web Service. There's a huge difference.
  4. Double-click your .svc.cs file and change the TODO item from a TODO comment to the actual classname of the object context created in step 2. In my case, this was FinanceManager.FinanceModel.
  5. Right-click the solution and choose "Add new Project", select "Silverlight Project".
  6. At this point, you should have a solution with a Silverlight project (make sure this builds), and a file-based ASP.NET web application that contains an entity data model. You should also have an Astoria service sitting on top of your EDM. To test things out before integrating Silverlight, build and run your app and hit the Astoria service, e.g. http://server/service.svc/tablename. You should get some XML showing you the contents of the table. If not, something went horribly wrong :) :)
  7. Now right-click the ASP.NET file-based web application and choose "Add Silverlight link". This will set your solution up so that your Silverlight app's DLL and any dependent DLLs will be copied to the client binary output directory of the ASP.NET application. You are not done!
  8. Drag a copy of silverlight.js from your Silverlight app to the ASP.NET app (you'll see why this is crucial shortly)
  9. Drag your TestPage.html file from the Silverlight app to your ASP.NET app. The reason you need to do this is because you will now be launching your Silverlight app from the ASP.NET app, not from the original Silverlight app location. This is because Silverlight cannot currently make cross-domain networking calls and you need to communicate using the BrowserWebHttpRequest object with the Astoria service.
  10. Now add some GUI to your Silverlight app, make a button responder, do some asynchronous stuff - all goodies you can find quick and dirty samples for elsewhere. Use the XmlReader object to consume the raw (no envelopes!! Down with WSDL!!) XML produced by the Astoria service.

In the end, I ended up with some "smoke test" (read: not yet pretty-fied) GUI that grabs Ledger entities from the Astoria service and uses the "ListBox" sample control from the SDK to do the rendering.

The transaction ID numbers and transactions actually came from my financial ledger service, which is an Astoria service sitting on top of an Entity Data Model.  

More to come!!

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More Stories By Kevin Hoffman

Kevin Hoffman, editor-in-chief of SYS-CON's iPhone Developer's Journal, has been programming since he was 10 and has written everything from DOS shareware to n-tier, enterprise web applications in VB, C++, Delphi, and C. Hoffman is coauthor of Professional .NET Framework (Wrox Press) and co-author with Robert Foster of Microsoft SharePoint 2007 Development Unleashed. He authors The .NET Addict's Blog at .NET Developer's Journal.

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.NET News 06/04/07 01:00:29 PM EDT

As you know, Silverlight is a new RIA enabling technology from Microsoft. Slightly less publicized but no less impactful is another technology from Microsoft - Astoria. Astoria is a tool that combines the power of the ADO.NET Entity Framework with the new enhanced power of RESTful POX services using WCF. In short, an Astoria service is a WCF service that sits on top of an Entity Model that allows you to hit services with URLs that look something like this: