c# - 在多播委托(delegate)上使用慢速 DynamicInvoke 的替代方法

Question

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(delegate)，其中调用目标包括不关心跨线程的小类，但也包括实现ISynchronizeInvoke并关心a的类很多关于跨线程，比如 Windows 窗体控件。

理论上，这段代码工作得很好，没有发生错误。但是 DynamicInvoke 非常慢，并不是说它是应用程序当前的瓶颈。

那么，我的问题来了:有没有什么方法可以在不破坏直接订阅事件的功能的情况下加速这个小功能？

所有事件/委托(delegate)的签名是(object sender, EventArgs param)

Answer 1

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，如果您使用的是 .NET3.5，则可以使用表达式树来获得一定程度的优化。我的示例使用 .NET4 中的并发字典，但它可以用普通字典和锁替换。

想法如下:委托(delegate)持有它正在调用的方法。对于调用的每个唯一方法，我创建(使用表达式树)调用该特定方法的已编译委托(delegate)。创建编译委托(delegate)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(delegate)就和普通委托(delegate)一样快。

在我的机器上，3,000,000 次调用使用编译委托(delegate)花费 1 秒，使用 DynamicInvoke 花费 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 运行时进行了编译)。

// 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 ();
        }
    }
}