Silverlight 4.0 Debugging Issue – “Unable to start Debugging.The Silverlight Developer Runtime Not Installed. Please Install a matching version” – Resolution

I have just encountered one issue while start the debugging one of my Silverlight 4 application. Silverlight 4.0 with VS 2010  was working fine few weeks back,  but today when I started debugging to test one of my application, I got the error message as below.


I thought, It may be the problem with the Silverlight version which is selected for this project. I checked the Silvelight “Target Silverlight Version”  from the Project Properties. But the Silvelight version was correct.


Then, I have also checked the associated hosting ASP.NET web application framework version. It was also targeting to .NET Framework 4.0 . So, there is no issue with my setup.


I started reinstalling the silverlight runtime and I received the below message 😦


I was bit confused and looking for some solution over internet, and finally got the resolution from the thread Unable to debug silverlight . ohh. It was due some wrong version installation. I installed the Silverlight 4 developer runtime from the mentioned link .


After installation, the issue got resolved.  🙂

But not sure, why there was the mismatch of silverlight runtime version as it was working fine few weeks back. 😦 . Sorry, I am not spending any time to investigate it right now! 🙂

Hope, This may help you and save your some amount of time.

Thanks !

.NET 4.0, Silverlight 4 ,


  1. Thank you so much for the blog. I also had the same problem. Everything was fine for months up until last week. Not sure what’s going on!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: