title: Can .NET 4.0 code interoperate with .NET 2.0 code?
body: <p>Are there compatibility barriers with a .NET 4.0 assembly calling code in a .NET 2.0 assembly?  And vice versa?</p>
  
  <p>More specifically, I'm investigating an upgrade to Visual Studio 2010 when using a third party application based on .NET 2.0.  The application is extensible by hooks that reference my custom code.  And vice versa, my code will reference the application's assemblies.</p>