Unable to start debugging. Check for one of the following. 1. The application you are trying to debug uses a version of the ...

Unable to start debugging.  Check for one of the following.

1. The application you are trying to debug uses a version of the Microsoft .NET Framework that is not supported by the debugger.
2. The debugger has made an incorrect assumption about the Microsoft .NET Framework version your application is going to use. 
3. The Microsoft .NET Framework version specified by you for debugging is incorrect.

Please see the Visual Studio .NET debugger documentation for correctly specifying the Microsoft .NET Framework version your application is going to use for debugging.