using System;

public class Program

{

    public static void Main()

    {

        Action<Foo> foo = val => Console.WriteLine("A: " + val.Baz);

        Action<Bar> bar = val => Console.WriteLine("B: " + val.Baz);

        var barInst = new Bar();

        var fooInst = new Foo();

        Act(foo, barInst);

        Act(bar, barInst);

        Act(foo, fooInst);

    }

    public static void Act<T>(Action<T> action, T data) where T : Foo {

        action(data);

    }

    public class Bar : Foo {

        public override string Baz {get{return "Bar";}}

    }

    public class Foo {

        public virtual string Baz {get{return "Foo";}}

    }

}