SQLCLR using the wrong version of the .NET Framework

Question

During a recent restart of our development server the SQL Server started using .NET 4.0 for the SQLCLR. This means that nothing using the CLR in SQ

Answer 1

Typically you can force a .NET application to use a specific .NET Framework version by specifying the supportedRuntime tag in the application's config file.

So you could try creating a sqlservr.exe.config in the \Binn folder under the root path of the SQL instance and specify there that you would like to use only .NET versions up to 3.5. Check this MSDN link for the structure of the config file.