Developing For .NET

I’m ready to begin my first production Silverlight 2 project, so I needed to learn how to make a data driven Silverlight application. I pretty much already knew that the answer would involve WCF, but as I do not have much experience with such things I was not sure what to expect. I had written several Web Services in PHP using NuSOAP, but I knew basically nothing about WCF or IIS hosting of web services. So, towards the goal of understanding what all the pieces are and how they fit together, I began my research.

Getting Started with WCF

As an old procedural midrange programmer, I always like to start with the data, so the WCF end was where I chose to begin. I tried watching Michele Bustamante’s 15 part video series on WCF, but half way through the second video my eyes glazed over and the drool was beginning to stain my shirt. While I understand she is a giant in the field, this series was not for the rank amateur.

I surfed around Google for a while and came up with several decent examples and a couple of videos. At some point, once I understood the basics, I stumbled across an example of the new Silverlight-enabled WCF Service item type which greatly simplified things. I hooked up a Linq to SQL project to my WCF service and was able to return Linq classes (or subsets as necessary).

I was able to hook up a simple WCF test inside a Silverlight 2 application and consume my new Services. All was well, but I had done everything inside the Silverlight project. It made more sense to me to break the WCF out into its own Solution. To accomplish this, I followed these steps:

1. Create a WCF Service Application
2. Delete the default Service1 files
3. Add a new “Silverlight-enabled WCF Service” item
4. Create the services as needed

Deploying the Service to IIS 6.0

I’m unfortunately still stuck with IIS 6.0. I don’t know if the experience is any different on IIS 7.0, but I went through some trials getting this to work properly. To be fair, I’m sure that most of the trials were caused by my own ignorance.

At first, I was trying to deploy the Services as part of an existing ASP.NET application. This got hairy pretty quickly, since I wasn’t sure how to properly merge the two projects together on the server. I tried deploying the Services to a subdirectory, but I could never get it to work. At that point I decided that it would probably be best if I put the services on their own subdomain, so I created a new subdomain for the Services.

I was able to deploy the Service site to the new subdomain and the WSDL page displayed properly. (Actually, it didn’t right away: I had apparently screwed something up trying to merge it with the other ASP.NET application, so I recreated the Service application from scratch which only took a few minutes. It was that page that displayed properly.)

So at this point I thought I should have been able to simply switch out my Service Reference in my Silverlight application, but it didn’t work. I messed around with it but couldn’t get it to respond. When I ran the application in debug, I received a message indicating that the WCF Service was not configured for cross domain access. Since the Service was now live on the domain but my application was running on localhost, my requests were being rejected by the server. To solve this, I added a clientaccesspolicy.xml file. At this point, the test Silverlight application running on my local machine began functioning again.

Deploying the Silverlight Application

Now, with my Service installed, configured, and running as desired, and with my Silverlight 2 application consuming that Service, I figured I was ready to deploy it to the server. I created my new ASP.NET web site on IIS 6.0 and deployed the Silverlight application’s test ASP.NET page. I pointed my browser to the test page and… nothing.

And by nothing, I mean I received the dreaded blank page. Even worse, when I tried to right-click to view the source, all I got was the “Silverlight Configuration” prompt. At first I was really bummed, but then I realized that if I was getting the Silverlight prompt, then that meant the browser recognized my content as Silverlight! I was actually closer to success than I originally imagined!

Once more unto the Google breach, and I found that, at least in IIS 6.0, you have to configure a MIME type for .xap files! I navigated to the MIME settings on my Silverlight domain and added a Type for extension “.xap” with a content type of “application/x-silverlight-app”. I restarted the web site and went to my page and Viola! I had a Silverlight 2 application running on IIS 6.0 that consumed WCF Services!

What’s next

So now that I have the basic structure down, I have a bit of work left to do. First, I need to test all my Services. Then I need to read up on performance for WCF: I believe there are some lazy loading techniques I can use to make sure my users are getting immediate access and not waiting around for a bunch of data to load. After that, it will be back to Blend 2 for some serious design work. I don’t have anything particularly juicy in mind for this application, but I do want something a little beyond the ordinary. Along the way, I’m hoping to upgrade to Server 2008, Sql Server 2008, and IIS 7.0. And in January I am taking Computer Graphics classes at the local community college. All in all, it looks like I’m going to be having a lot of fun in the near future!