I recently attempted to open a Visual Studio solution that someone sent me.  I kept getting this error when I opened it...

‘C:\myprojfile.csproj’ cannot be opened because its project type (.csproj) is not supported by this version of the application.  To open it, please use a version that supports this type of project.

After a little digging, I found that this solution worked great for me:

1. Open Visual Studio Command Prompt (Start&gt; All Programs &gt; Visual Studio 20## &gt; Visual Studio Tools &gt; Click Visual Studio 20## Command Prompt)
2. Type in 'devenv.exe /resetskippkgs' without the quotes and hit enter
3. Visual Studio should open and you should be able to open and convert the solution and/or project now.