在多播委托上使用慢速 DynamicInvoke 的替代方案

我在基类中有以下代码：

public static void InvokeExternal(Delegate d, object param, object sender)
{
    if (d != null)
    {
        //Check each invocation target
        foreach (Delegate dDelgate in d.GetInvocationList())
        {
            if (dDelgate.Target != null && dDelgate.Target is System.ComponentModel.ISynchronizeInvoke
                && ((System.ComponentModel.ISynchronizeInvoke)(dDelgate.Target)).InvokeRequired)
            {
                //If target is ISynchronizeInvoke and Invoke is required, invoke via ISynchronizeInvoke
                ((System.ComponentModel.ISynchronizeInvoke)(dDelgate.Target)).Invoke(dDelgate, new object[] { sender, param });
            }
            else
            {
                //Else invoke dynamically
                dDelgate.DynamicInvoke(sender, param);
            }
        }
    }
}

此代码示例负责调用一个事件，表示为多播委托，其中调用目标包括不关心跨线程的小类，还包括实现ISynchronizeInvoke并且非常关心跨线程，例如 Windows 窗体控件。

理论上，这个片段工作得很好，没有错误发生。但是DynamicInvoke速度非常慢，并不是说它是应用程序当前的瓶颈。

所以，我的问题是：有什么方法可以加速这个小功能而不破坏直接订阅事件的功能吗？

所有活动/代表的签名是(object sender, EventArgs param)

如果 dDelegate 是已知类型（即 Action），您始终可以转换为它并直接调用它。

话虽如此，如果您使用 .NET3.5，您可以使用表达式树来获得相当多的优化。我的示例使用 .NET4 中的并发字典，但这可以用普通字典和锁替换。

这个想法如下：委托保存它正在调用的方法。对于每个被调用的独特方法，我创建（使用表达式树）一个调用该特定方法的已编译委托。创建编译委托的成本很高，这就是缓存它很重要的原因，但一旦创建，编译委托就和普通委托一样快。

在我的机器上，3,000,000 个调用使用已编译的委托花费了 1 秒，使用 DynamicInvoke 花费了 16 秒。

// Comment this line to use DynamicInvoke instead as a comparison
#define USE_FAST_INVOKE


namespace DynInvoke
{
    using System;
    using System.Collections.Concurrent;
    using System.Linq.Expressions;
    using System.Reflection;

    static class Program
    {
        delegate void CachedMethodDelegate (object instance, object sender, EventArgs param);

        readonly static ConcurrentDictionary<MethodInfo, CachedMethodDelegate> s_cachedMethods =
            new ConcurrentDictionary<MethodInfo, CachedMethodDelegate> ();

        public static void InvokeExternal(Delegate d, object sender, EventArgs param)
        {
            if (d != null)
            {
                //Check each invocation target            
                foreach (var dDelgate in d.GetInvocationList())
                {
                    if (
                            dDelgate.Target != null
                        &&  dDelgate.Target is System.ComponentModel.ISynchronizeInvoke
                        &&  ((System.ComponentModel.ISynchronizeInvoke)(dDelgate.Target)).InvokeRequired
                        )
                    {
                        //If target is ISynchronizeInvoke and Invoke is required, invoke via ISynchronizeInvoke                    
                        ((System.ComponentModel.ISynchronizeInvoke)(dDelgate.Target)).Invoke(dDelgate, new object[] { sender, param });
                    }
                    else
                    {
#if USE_FAST_INVOKE
                        var methodInfo = dDelgate.Method;

                        var del = s_cachedMethods.GetOrAdd (methodInfo, CreateDelegate);

                        del (dDelgate.Target, sender, param);
#else
                        dDelgate.DynamicInvoke (sender, param);
#endif
                    }
                }
            }
        }

        static CachedMethodDelegate CreateDelegate (MethodInfo methodInfo)
        {
            var instance = Expression.Parameter (typeof (object), "instance");
            var sender = Expression.Parameter (typeof (object), "sender");
            var parameter = Expression.Parameter (typeof (EventArgs), "parameter");

            var lambda = Expression.Lambda<CachedMethodDelegate>(
                Expression.Call (
                    Expression.Convert (instance, methodInfo.DeclaringType),
                    methodInfo,
                    sender,
                    parameter
                    ),
                instance,
                sender,
                parameter
                );

            return lambda.Compile ();
        }

        class MyEventListener
        {
            public int Count;

            public void Receive (object sender, EventArgs param)
            {
                ++Count;
            }
        }

        class MyEventSource
        {
            public event Action<object, EventArgs> AnEvent;

            public void InvokeAnEvent (EventArgs arg2)
            {
                InvokeExternal (AnEvent, this, arg2);
            }
        }

        static void Main(string[] args)
        {

            var eventListener = new MyEventListener ();
            var eventSource = new MyEventSource ();

            eventSource.AnEvent += eventListener.Receive;

            var eventArgs = new EventArgs ();
            eventSource.InvokeAnEvent (eventArgs);

            const int Count = 3000000;

            var then = DateTime.Now;

            for (var iter = 0; iter < Count; ++iter)
            {
                eventSource.InvokeAnEvent (eventArgs);
            }

            var diff = DateTime.Now - then;

            Console.WriteLine (
                "{0} calls took {1:0.00} seconds (listener received {2} calls)", 
                Count, 
                diff.TotalSeconds,
                eventListener.Count
                );

            Console.ReadKey ();
        }
    }
}

编辑：由于OP使用.NET2，我添加了一个应该与.NET2运行时兼容的示例（因为我使用VS2010，我可能会错误地使用一些新的语言功能，但我确实使用.NET2运行时进行编译）。

// Comment this line to use DynamicInvoke instead as a comparison
#define USE_FASTER_INVOKE

namespace DynInvoke
{
    using System;
    using System.Globalization;
    using System.Reflection.Emit;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Reflection;

    static class FasterInvoke
    {
        delegate void CachedMethodDelegate (object instance, object sender, EventArgs param);

        readonly static Dictionary<MethodInfo, CachedMethodDelegate> s_cachedMethods =
            new Dictionary<MethodInfo, CachedMethodDelegate> ();

        public static void InvokeExternal (Delegate d, object sender, EventArgs param)
        {
            if (d != null)
            {
                Delegate[] invocationList = d.GetInvocationList ();
                foreach (Delegate subDelegate in invocationList)
                {
                    object target = subDelegate.Target;
                    if (
                        target != null
                        && target is ISynchronizeInvoke
                        && ((ISynchronizeInvoke)target).InvokeRequired
                        )
                    {
                        ((ISynchronizeInvoke)target).Invoke (subDelegate, new[] { sender, param });
                    }
                    else
                    {
#if USE_FASTER_INVOKE
                        MethodInfo methodInfo = subDelegate.Method;

                        CachedMethodDelegate cachedMethodDelegate;
                        bool result;

                        lock (s_cachedMethods)
                        {
                            result = s_cachedMethods.TryGetValue (methodInfo, out cachedMethodDelegate);
                        }

                        if (!result)
                        {
                            cachedMethodDelegate = CreateDelegate (methodInfo);
                            lock (s_cachedMethods)
                            {
                                s_cachedMethods[methodInfo] = cachedMethodDelegate;
                            }
                        }

                        cachedMethodDelegate (target, sender, param);
#else
                        subDelegate.DynamicInvoke (sender, param);
#endif
                    }
                }
            }
        }

        static CachedMethodDelegate CreateDelegate (MethodInfo methodInfo)
        {
            if (!methodInfo.DeclaringType.IsClass)
            {
                throw CreateArgumentExceptionForMethodInfo (
                    methodInfo, 
                    "Declaring type must be class for method: {0}.{1}"
                    );
            }


            if (methodInfo.ReturnType != typeof (void))
            {
                throw CreateArgumentExceptionForMethodInfo (
                    methodInfo,
                    "Method must return void: {0}.{1}"
                    );
            }

            ParameterInfo[] parameters = methodInfo.GetParameters ();
            if (parameters.Length != 2)
            {
                throw CreateArgumentExceptionForMethodInfo (
                    methodInfo,
                    "Method must have exactly two parameters: {0}.{1}"
                    );
            }


            if (parameters[0].ParameterType != typeof (object))
            {
                throw CreateArgumentExceptionForMethodInfo (
                    methodInfo,
                    "Method first parameter must be of type object: {0}.{1}"
                    );
            }

            Type secondParameterType = parameters[1].ParameterType;
            if (!typeof (EventArgs).IsAssignableFrom (secondParameterType))
            {
                throw CreateArgumentExceptionForMethodInfo (
                    methodInfo,
                    "Method second parameter must assignable to a variable of type EventArgs: {0}.{1}"
                    );
            }

            // Below is equivalent to a method like this (if this was expressible in C#):
            //  void Invoke (object instance, object sender, EventArgs args)
            //  {
            //      ((<%=methodInfo.DeclaringType%>)instance).<%=methodInfo.Name%> (
            //          sender,
            //          (<%=secondParameterType%>)args
            //          );
            //  }

            DynamicMethod dynamicMethod = new DynamicMethod (
                String.Format (
                    CultureInfo.InvariantCulture,
                    "Run_{0}_{1}",
                    methodInfo.DeclaringType.Name,
                    methodInfo.Name
                    ),
                null,
                new[]
                    {
                        typeof (object),
                        typeof (object),
                        typeof (EventArgs)
                    },
                true
                );

            ILGenerator ilGenerator = dynamicMethod.GetILGenerator ();
            ilGenerator.Emit (OpCodes.Ldarg_0);
            ilGenerator.Emit (OpCodes.Castclass, methodInfo.DeclaringType);
            ilGenerator.Emit (OpCodes.Ldarg_1);
            ilGenerator.Emit (OpCodes.Ldarg_2);
            ilGenerator.Emit (OpCodes.Isinst, secondParameterType);
            if (methodInfo.IsVirtual)
            {
                ilGenerator.EmitCall (OpCodes.Callvirt, methodInfo, null);                
            }
            else
            {
                ilGenerator.EmitCall (OpCodes.Call, methodInfo, null);                
            }
            ilGenerator.Emit (OpCodes.Ret);

            return (CachedMethodDelegate)dynamicMethod.CreateDelegate (typeof (CachedMethodDelegate));
        }

        static Exception CreateArgumentExceptionForMethodInfo (
            MethodInfo methodInfo, 
            string message
            )
        {
            return new ArgumentException (
                String.Format (
                    CultureInfo.InvariantCulture,
                    message,
                    methodInfo.DeclaringType.FullName,
                    methodInfo.Name
                    ),
                "methodInfo"
                );
        }
    }

    static class Program
    {
        class MyEventArgs : EventArgs
        {

        }

        class MyEventListener
        {
            public int Count;

            public void Receive (object sender, MyEventArgs param)
            {
                ++Count;
            }
        }

        delegate void MyEventHandler (object sender, MyEventArgs args);

        class MyEventSource
        {
            public event MyEventHandler AnEvent;

            public void InvokeAnEvent (MyEventArgs arg2)
            {
                FasterInvoke.InvokeExternal (AnEvent, this, arg2);
            }
        }

        static void Main (string[] args)
        {
            MyEventListener eventListener = new MyEventListener ();
            MyEventSource eventSource = new MyEventSource ();

            eventSource.AnEvent += eventListener.Receive;

            MyEventArgs eventArgs = new MyEventArgs ();
            eventSource.InvokeAnEvent (eventArgs);

            const int count = 5000000;

            DateTime then = DateTime.Now;

            for (int iter = 0; iter < count; ++iter)
            {
                eventSource.InvokeAnEvent (eventArgs);
            }

            TimeSpan diff = DateTime.Now - then;

            Console.WriteLine (
                "{0} calls took {1:0.00} seconds (listener received {2} calls)",
                count,
                diff.TotalSeconds,
                eventListener.Count
                );

            Console.ReadKey ();
        }
    }
}