I just thought I'd pass this on from Wesner Moise's .NET Undocumented blog: Open Generic Types seem to be an undocumented feature in C# 2.0 that might be quite useful for Reflection-related work. Basically, it allows the handling of Generic types that haven't been "closed", i.e. it's still unknown which other type(s) the Generic type is supposed to work with. Read it, it's interesting!