A constrained generic delegate in C#

Question

I would like to have a delegate that is constrained to returning one of two types; an ActionResult or a string. Is this possible?

Answer 1

No, it's not possible (at least not in C# 4 and below). There's no support for "or" constraints on generic type parameters.

There's also no constraint that restricts a type argument to be an exact type. All constraints restrict the base types of the type argument. They cannot restrict you from inheriting from them.