App crashes when File Upload Dialog is Closed

Dec 13, 2011 at 2:21 PM

I am using the quick start example in Silverlight 4.  I can upload a file successfully (shows 100% and file is really uploaded).  However, when I close the dialog window that shows progress, I get the following Visual Studio Just-In-Time Debugger message: "An unhandled exception ("Unhandled Error in Silverlight Application Code 4004. Category: Managed RuntimeError. Message: System.NullReferenceException: [Arg_NullReferenceException].  The error dialog also give me a choice of debuggers.  I am running VS 2010, SP1 with Development Server (not IIS).

Dec 13, 2011 at 5:28 PM

This is the first i've had someone encounter this. Sounds like it might be environmental. What browser are you using and are you running out of browser when this happens? There is an issue with FF and SL OOB while in debug mode.

Dec 13, 2011 at 8:12 PM

IE9.  I am not running out of browser.

Dec 13, 2011 at 8:15 PM

Are you do anythinng special or are you running the raw quick start code?

Dec 14, 2011 at 4:30 PM

I am not doing anything special. I am just trying to get the quick start to work.

Dec 14, 2011 at 4:35 PM

Can you try running this site and see if you get the error?

This is the demo application that's included with the source code.

Dec 14, 2011 at 4:49 PM

The demo works fine - no crashes.

Dec 14, 2011 at 5:15 PM

OK, I created a new project from scratch and followed the quick start tutorial (albeit I fixed the documentation as the handler source code had the wrong class namespace and in the onerror it referenced the HSS.Logging so I removed that too) and used the code and config 100% as shown and ran it and no errors. I'm using VS 2010 sp1, IE9 on Win7.

I realize this doesn't help you, but I'm unable to replicate, so if you could provide more details, I could figure something out.

Dec 14, 2011 at 5:38 PM

I've uploaded my test solution ( to

Maybe download that project and see if the error still occurs...

Dec 14, 2011 at 9:08 PM

I deleted all other instances of SLFileUploadTest, Downloaded your zip file, unzipped, and unblocked all files that were blocked by Windows 7.  I ran the app and got the same result - choose a new instance of vs or Script Editor