Problems with debugging in Silverlight 4 using Out of Browser and WCF RIA Services

Question

With Visual stuido 2010, it's simple to set up SL4 to debug with an out-of-browser installed app. I followed the instructions from here and everything seems to set up fine. Debugging from the browser runs the program just fine, but running from the OOB program gives a different result. After starting, the screen will go blank and then hang forever. I have some concerns that it might be because of some of the technologies that we're using.

Firstly, there's a popup that happens because we're using WCF RIA Services (formerly .NET RIA Services).

"RIA Services will fail unless the silverlight project is hosted and launched from the same web project that contains the RIA Services."

This seems to just be a warning, but I have a suspicion that this warning might be telling me that RIA Services needs to have the .web project as its startup project.

We're also using prism and the error has an odor of a Prism error too. (something loading and then not ever appearing)

Has anyone else had any issues with OOB debugging in SL4? Is anyone else OOB debugging in SL4?

Sorry it's so vague. It's a complicated mess. The only message I see is the italicized popup warning. Then the window (which was previously showing the background of our application) just goes blank

Answer 1

There is currently a known issue with debugging an Out of Browser Silverlight 4 application when using F5 to launch the application from within VS 2010. The question I have is whether or not the application launches without debugging (-F5 or running it from the shortcut)? In the case of using F5, a dialog typically appears with the following error dialog “Unable to start debugging. A fatal error occured. For more details, please see the Microsoft Help and Support web site. HRESULT=0x80070018” and then the application appears to hang. In this case detaching allows the process to continue and then reattaching should allow you to debug the process.

If this is completely blocking or you’re trying to debug code running at startup (like the page startup event), one possible way to get around this would be to put in a call to System.Diagnostics.Debugger.Break, start the program and then attach when dialog pops.

Answer 2

This can be caused by the OOBA install being older than the version you are trying to debug. Remember, Silverlight OOBAs do not automatically update themselves to the latest version of the XAP file that may be available on the server. You have to update them yourself. If you get this error and you have included the auto-update logic in your app, just bounce out of VS, run the app so it auto-updates, then go back in and debug.

Alternately, you can uninstall the app and re-install it. That will ensure you are debugging against the latest VS build.

I ran into this same issue with VS 2008 and Silverlight 3. If I got it, I just jumped out and updated the app then re-ran it in VS and had full debugging.