Question

I want to call a generic method that constrains the input type T to implement two interfaces:

interface IA { }
interface IB { }
void foo<T>(T t) where T : IA, IB { }

How can I fix the last line of

void bar(object obj)
{
    if (obj is IA && obj is IB)
    {
        foo((IA && IB)obj);
    }
}

?

Reflection probably allows to do the call, but I would like to stay within the language.

Answer 1

Does the C# 4.0 dynamic keyword get you out of jail (mostly) free? After all – you are already doing the type checking.

interface IC : IA, IB { }

void bar(object obj)
{
  if (obj is IA && obj is IB)
  {
    IC x = (dynamic)obj;
    foo(x);
  }
}

Does that break if foo tries to cast the parameter to T? I don’t know.