C# – Inherit from a generic base class, apply a constraint, and implement an interface in C#


This is a syntax question. I have a generic class which is inheriting from a generic base class and is applying a constraint to one of the type parameters. I also want the derived class to implement an interface. For the life of me, I cannot seem to figure out the correct syntax.

This is what I have:

DerivedFoo<T1,T2> : ParentFoo<T1, T2> where T2 : IBar { ... }

The first thing that came to mind was this:

DerivedFoo<T1,T2> : ParentFoo<T1, T2> where T2 : IBar, IFoo { ... }

But that is incorrect as that causes T2 to need to implement both IBar and IFoo, not DerivedFoo to implement IFoo.

I've tried a bit of Googling, use of colons, semicolons, etc, but I've turned up short. I'm sure the answer is head slappingly simple.

Best Solution

You include the entire signature of your class before you define generic constraints.

class DerivedFoo<T1, T2> : ParentFoo<T1, T2>, IFoo where T2 : IBar