反射性能优化 FastMethodInvoker（不是原创）

using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;

namespace FastMethodInvoker
{
    public delegate object FastInvokeHandler(object target, object[] paramters);

    public delegate void SayHandler(string word);

    class Program
    {

        static object InvokeMethod(FastInvokeHandler invoke, object target, params object[] paramters)
        {
            return invoke(null, paramters);
        }

        static void Main(string[] args)
        {

            Type t = typeof(Person);
            MethodInfo methodInfo = t.GetMethod("Say");
            Person person = new Person();
            string word = "hello";
            Person p = null;
            object[] param = new object[] { word, p, 3 };

            Stopwatch watch = new Stopwatch();
            watch.Start();
            for (int i = 0; i < 1000000; i++)
            {
                methodInfo.Invoke(person, param);
            }
            watch.Stop();
            Console.WriteLine("1000000 times invoked by Reflection: " + watch.ElapsedMilliseconds + "ms");

            Stopwatch watch1 = new Stopwatch();
            FastInvokeHandler fastInvoker = GetMethodInvoker(methodInfo);
            watch1.Start();
            for (int i = 0; i < 1000000; i++)
            {
                fastInvoker(person, param);
            }
            watch1.Stop();
            Console.WriteLine("1000000 times invoked by FastInvoke: " + watch1.ElapsedMilliseconds + "ms");

            Stopwatch watch2 = new Stopwatch();
            watch2.Start();
            for (int i = 0; i < 1000000; i++)
            {
                person.Say(ref word, out p, 3);
            }
            watch2.Stop();
            Console.WriteLine("1000000 times invoked by DirectCall: " + watch2.ElapsedMilliseconds + "ms");

            Console.ReadLine();
        }

        private static FastInvokeHandler GetMethodInvoker(MethodInfo methodInfo)
        {
            DynamicMethod dynamicMethod = new DynamicMethod(string.Empty, typeof(object), new Type[] { typeof(object), typeof(object[]) }, methodInfo.DeclaringType.Module);
            ILGenerator il = dynamicMethod.GetILGenerator();
            ParameterInfo[] ps = methodInfo.GetParameters();
            Type[] paramTypes = new Type[ps.Length];
            for (int i = 0; i < paramTypes.Length; i++)
            {
                if (ps[i].ParameterType.IsByRef)
                    paramTypes[i] = ps[i].ParameterType.GetElementType();
                else
                    paramTypes[i] = ps[i].ParameterType;
            }
            LocalBuilder[] locals = new LocalBuilder[paramTypes.Length];

            for (int i = 0; i < paramTypes.Length; i++)
            {
                locals[i] = il.DeclareLocal(paramTypes[i], true);
            }
            for (int i = 0; i < paramTypes.Length; i++)
            {
                il.Emit(OpCodes.Ldarg_1);
                EmitFastInt(il, i);
                il.Emit(OpCodes.Ldelem_Ref);
                EmitCastToReference(il, paramTypes[i]);
                il.Emit(OpCodes.Stloc, locals[i]);
            }
            if (!methodInfo.IsStatic)
            {
                il.Emit(OpCodes.Ldarg_0);
            }
            for (int i = 0; i < paramTypes.Length; i++)
            {
                if (ps[i].ParameterType.IsByRef)
                    il.Emit(OpCodes.Ldloca_S, locals[i]);
                else
                    il.Emit(OpCodes.Ldloc, locals[i]);
            }
            if (methodInfo.IsStatic)
                il.EmitCall(OpCodes.Call, methodInfo, null);
            else
                il.EmitCall(OpCodes.Callvirt, methodInfo, null);
            if (methodInfo.ReturnType == typeof(void))
                il.Emit(OpCodes.Ldnull);
            else
                EmitBoxIfNeeded(il, methodInfo.ReturnType);

            for (int i = 0; i < paramTypes.Length; i++)
            {
                if (ps[i].ParameterType.IsByRef)
                {
                    il.Emit(OpCodes.Ldarg_1);
                    EmitFastInt(il, i);
                    il.Emit(OpCodes.Ldloc, locals[i]);
                    if (locals[i].LocalType.IsValueType)
                        il.Emit(OpCodes.Box, locals[i].LocalType);
                    il.Emit(OpCodes.Stelem_Ref);
                }
            }

            il.Emit(OpCodes.Ret);
            FastInvokeHandler invoder = (FastInvokeHandler)dynamicMethod.CreateDelegate(typeof(FastInvokeHandler));
            return invoder;
        }

        private static void EmitCastToReference(ILGenerator il, System.Type type)
        {
            if (type.IsValueType)
            {
                il.Emit(OpCodes.Unbox_Any, type);
            }
            else
            {
                il.Emit(OpCodes.Castclass, type);
            }
        }

        private static void EmitBoxIfNeeded(ILGenerator il, System.Type type)
        {
            if (type.IsValueType)
            {
                il.Emit(OpCodes.Box, type);
            }
        }

        private static void EmitFastInt(ILGenerator il, int value)
        {
            switch (value)
            {
                case -1:
                    il.Emit(OpCodes.Ldc_I4_M1);
                    return;
                case 0:
                    il.Emit(OpCodes.Ldc_I4_0);
                    return;
                case 1:
                    il.Emit(OpCodes.Ldc_I4_1);
                    return;
                case 2:
                    il.Emit(OpCodes.Ldc_I4_2);
                    return;
                case 3:
                    il.Emit(OpCodes.Ldc_I4_3);
                    return;
                case 4:
                    il.Emit(OpCodes.Ldc_I4_4);
                    return;
                case 5:
                    il.Emit(OpCodes.Ldc_I4_5);
                    return;
                case 6:
                    il.Emit(OpCodes.Ldc_I4_6);
                    return;
                case 7:
                    il.Emit(OpCodes.Ldc_I4_7);
                    return;
                case 8:
                    il.Emit(OpCodes.Ldc_I4_8);
                    return;
            }

            if (value > -129 && value < 128)
            {
                il.Emit(OpCodes.Ldc_I4_S, (SByte)value);
            }
            else
            {
                il.Emit(OpCodes.Ldc_I4, value);
            }
        }
    }

    public class Person
    {
        public void Say(ref string word, out Person p, int avi)
        {
            word = "ttt" + avi.ToString();
            p = new Person();
        }
    }
}