using System;

class P
{
    static void Main()
    {
        Foo(x => x.X() as object);
    }

    static extern void Foo(Func<A, object> x);
    static extern void Foo(Func<B, object> x);

}

class A
{
    public Func<int> X { get; set; }
}

class B
{
    public extern void X();
}