plugins in .NET (C#, VB Development)

This is no longer the case with .NET 4.0 with the Side-by-Side support.

from Peter Ritchie's MVP blog

Another notable improvement is side-by-side (SxS) support for multiple versions of .NET. This allows hosting of more than one version of the CLR within a single process. This makes writing shell extensions, for example, in C# a reality in .NET 4.0. You shouldn't need to target .NET 4.0, but as long as .NET 4.0 is installed you should be able to write shell extensions in a current version of .NET (like .NET 2.0) and it will be supported. Prior to .NET 4.0, a process could only have one version of the CLR loaded into a process, making extending 3rd party native applications (like the Windows shell) very problematic because what version of the CLR that was loaded into a process would depend on the first extension loaded. If the first extension loaded was a .NET 1.1 assembly then any other extensions loaded requiring .NET 2.0 would subsequently fail.

http://msmvps.com/blogs/peterritchie/arc...pment.aspx