using System;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Reflection;

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            var mi = typeof(A).GetMethod("Foo");

            Console.WriteLine("Regular method");
            Time(() => new A().Foo(1, 2));
            Console.WriteLine();

            Console.WriteLine("Invoke");
            Time(() => mi.Invoke(new A(), new object[] { 1, 2 }));
            Console.WriteLine();

            Console.WriteLine("Cached Delegate");
            var cache = Compile(mi);
            Time(() => cache.Invoke(new A(), 1, 2));
            Console.WriteLine();

            Console.WriteLine("Open Delegate");
            var od = CreateOpenDelegate(mi);
            Time(() => od.Invoke(new A(), 1, 2));
        }

        private static void Time(Action a)
        {
            var sw = Stopwatch.StartNew();
            for (int i = 0; i < 10000000; i++)
            {
                a();
            }
            sw.Stop();
            Console.WriteLine(sw.Elapsed);
        }

        private static Action<A, int, int> Compile(MethodInfo mi)
        {
            // Params
            var p1 = Expression.Parameter(typeof(A));
            var p2 = Expression.Parameter(typeof(int));
            var p3 = Expression.Parameter(typeof(int));

            // Body
            var body = Expression.Call(p1, mi, p2, p3);

            // compile
            return Expression.Lambda<Action<A, int, int>>(body, p1, p2, p3).Compile();
        }

        private static Action<A, int, int> CreateOpenDelegate(MethodInfo mi)
        {
            var openDelegate = Delegate.CreateDelegate(
                typeof(Action<A, int, int>),
                null,
                mi,
                true);

            return (Action<A, int, int>)openDelegate;
        }
    }

    public class A
    {
        public void Foo(int a, int b)
        {
        }
    }
}