Silverlight 3 debugging error in Visual Studio 2010

“Unable to start debugging. The application uses a version of Silverlight that is not supported by the debugger.”

Yeah, got that one. It’s actually a pretty clear error message once you understand a few things.

First, debugging Silverlight applications requires the Developer Runtime version of Silverlight. If Visual Studio installs Silverlight for you, you will get the developer version. However, since you’re somewhat likely to already have Silverlight on your computer, VS won’t install it, and you’re left without the developer version.

The developer version is easy to get from the Silverlight site, but the problem is that you’re likely to get the Silverlight 4 Developer Runtime. That won’t help you in debugging Silverlight 3 applications, so you need the Silverlight 3 developer runtime, which is considerably harder to find.

Here are the direct download links: Silverlight 3 Developer Runtime (~6.4 megs) and Silverlight 4 Developer Runtime (~8.2 megs). The sizes are important as all versions are named as Silverlight_developer.exe, and the only easy way you can tell them apart is by the file sizes.

Also note that you cannot install Silverlight 3 runtime after you’ve got version 4, so you may end up temporarily uninstalling Silverlight 4 before you install Silverlight 3. But a few reboots later, Silverlight 3 is working. At least for me, at least for now.

May 4, 2010 · Jouni Heikniemi · One Comment
Tags: ,  · Posted in: .NET

One Response

  1. Andreas - May 20, 2010

    Thanks! This really helped me.

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