delegate callbacks to interop

using System;
using System.Runtime.InteropServices;

class Demo
{
    static int Add(int left, int right) {
        return left + right;
    }
    [DllImport("MyLibrary.dll")]
    static extern void Foo(Func<int, int, int> func, bool bar);
    ...

    static void Main() {
        // call C++ with a delegate pointing to your method
        Foo(Add, true);
    }

}