.Net4.0用表达式树构建委托改善反射性能

转自:  http://www.cnblogs.com/lemontea/archive/2013/02/04/2891281.html

最近搞一个系统时由于在比较关键地方用到反射了，所以要关注了一下反射的性能问题。

.Net4.0反射性能改善

看老赵的文章，老赵得到的结果是这样的：

00:00:00.0125539 (Directly invoke)00:00:04.5349626 (Reflection invoke)00:00:00.0322555 (Dynamic executor)

而我把代码搞下来自己运行得到这样的结果：

这里不是说机器性能造成绝对的时间，而是差距比例完全不一样，想了一阵想起了老赵当时应该是基于.Net3.5，果断把程序的目标框架切换到.Net3.5，结果如下：

00:00:00.0018801 (Directly invoke)00:00:02.4288876 (Reflection invoke)00:00:00.0141537 (Dynamic executor)

三者的差距仍然有些不一样，老赵那边的直接调用与动态执行同一数量级的结果还是没有。但发现了另一些信息。反射和直接调用方法.Net4.0比.Net3.5有非常大的改善，特别是反射，性能提升了好几倍。反而构建表达式树动态调用的方式性能比.Net3.5差了一点。但是相对反射还是有差距，按照这个比例，写写表达式树还是值得的。

改善老赵的DynamicMethodExecutor

老赵的那篇的文章的思路是使用DynamicMethodExecutor来构造一个万能的委托Func<object, object[], object>其中第一个参数是实例对象，第二是参数列表，第三是返回值。.Net4.0的表达式树要比3.5的先进一点，经过一番改造发现是不需要这么一个万能委托的，直接用Expression.Lambda.Compile()编译出来的Delegate强制转换为强类型的委托来得更加简单。全部代码一个方法即可，精简了许多。

/// <summary>/// 动态构造委托/// </summary>/// <param name="methodinfo">方法元数据</param>/// <returns>委托</returns>public static Delegate BuildDynamicDelegate(MethodInfo methodInfo){    if (methodInfo == null)        throw new ArgumentNullException("methodInfo");    var paramExpressions = methodInfo.GetParameters().Select((p, i) =>    {        var name = "param" + (i + 1).ToString(CultureInfo.InvariantCulture);        return Expression.Parameter(p.ParameterType, name);    }).ToList();    MethodCallExpression callExpression;    if (methodInfo.IsStatic)    {        //Call(params....)        callExpression = Expression.Call(methodInfo, paramExpressions);    }    else    {        var instanceExpression = Expression.Parameter(methodInfo.ReflectedType, "instance");        //insatnce.Call(params….)        callExpression = Expression.Call(instanceExpression, methodInfo, paramExpressions);        paramExpressions.Insert(0, instanceExpression);    }    var lambdaExpression = Expression.Lambda(callExpression, paramExpressions);    return lambdaExpression.Compile();}

使用时转换为强类型的委托即可：

var action = (Action<TInstance, T1, T2>)BuildDynamicDelegate(methodInfo);var func = (Func<TInstance, T1, T2, TReturn>)BuildDynamicDelegate(methodInfo);老赵那个委托都是object，使用时的类型转换，还有装箱，拆箱都会有一定的性能损失，而强类型就没有这个问题。首先在老赵的那篇文章上一个方法改为两个方法，然后测试：public void Call1(object o1, object o2, object o3) { }public void Call2(int o1, int o2, int o3) { }private static void DynamicExecutor_ObjectType(){    var executor = new DynamicMethodExecutor(Call1MethodInfo);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        executor.Execute(ProgramInstance, ObjectParameters);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic executor(object))(JeffreyZhao)");}private static void DynamicExecutor_IntType(){    var executor = new DynamicMethodExecutor(Call2MethodInfo);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        executor.Execute(ProgramInstance, IntParameters);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic executor(int))(JeffreyZhao)");}private static void DynamicExecutor_StrongObject(){    var action = DynamicMethodBuilder.BuildAction<Program, object, object, object>(Call1MethodInfo);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        action(ProgramInstance, ObjectParameters[0], ObjectParameters[1], ObjectParameters[2]);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic executor(object))(zhangweiwen)");}private static void DynamicExecutor_StrongInt(){    var action = DynamicMethodBuilder.BuildAction<Program, int, int, int>(Call2MethodInfo);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        action(ProgramInstance, IntParameters1[0], IntParameters1[1], IntParameters1[2]);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic executor(int))(zhangweiwen)");}

结果：

00:00:00.0188422 (Dynamic executor(object))(JeffreyZhao)00:00:00.0210869 (Dynamic executor(int))(JeffreyZhao)00:00:00.0142841 (Dynamic executor(object))(zhangweiwen)00:00:00.0147589 (Dynamic executor(int))(zhangweiwen)

差距不大，但是还是有一定得改善，特别参数是int的方法，用了强类型后性能比较稳定，不会出现偏差。

构建委托动态赋值

既然有动态调用方法，同样也可以动态赋值，而且据我的经验，根据PropertyInfo的SetValue去反射设属性值用得比反射调用方法更加频繁。所以同样需要有方法来动态构建委托改善性能。

幸好，.Net4.0提供了支持，.Net4.0新增了Expression.Assign来表示一个赋值表达式。有了它，构建起来比方法的更加简单：

private static Action<TInstance, TProperty> BuildSetPropertyAction<TInstance, TProperty>(PropertyInfo propertyInfo){    var instanceParam = Expression.Parameter(typeof(TInstance), "instance");    var valueParam = Expression.Parameter(typeof(TProperty), "value");    //instance.Property    var propertyProperty = Expression.Property(instanceParam, propertyInfo);    //instance.Property = value    var assignExpression = Expression.Assign(propertyProperty, valueParam);    var lambdaExpression = Expression.Lambda<Action<TInstance, TProperty>>(assignExpression, instanceParam, valueParam);    return lambdaExpression.Compile();}

直接返回了强类型的委托，所以使用起来更加简单：

var action = BuildSetPropertyAction<Program, object>(ObjectPropertyInfo);action(ProgramInstance, ObjectValue);

来测试一下性能：

private static void DirectlySetValueType(){    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        ProgramInstance.IntProperty = IntValue;    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Directly Set IntProperty)");}private static void ReflectionSetValueType(){    var watch2 = new Stopwatch();    watch2.Start();    for (var i = 0; i < Times; i++)    {        IntPropertyInfo.SetValue(ProgramInstance, IntValue, null);    }    watch2.Stop();    Console.WriteLine(watch2.Elapsed + " (Reflection Set IntProperty)");}private static void DynamicSetValueType(){    var action = BuildSetPropertyAction<Program, int>(IntPropertyInfo);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        action(ProgramInstance, IntValue);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic Set IntProperty)");}private static void DirectlySetReferenceType(){    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        ProgramInstance.ObjectProperty = ObjectValue;    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Directly Set ObjectProperty)");}private static void ReflectionSetReferenceType(){    var watch2 = new Stopwatch();    watch2.Start();    for (var i = 0; i < Times; i++)    {        ObjectPropertyInfo.SetValue(ProgramInstance, ObjectValue, null);    }    watch2.Stop();    Console.WriteLine(watch2.Elapsed + " (Reflection Set ObjectProperty)");}private static void DynamicSetReferenceType(){    var action = BuildSetPropertyAction<Program, object>(ObjectPropertyInfo);    //action(ProgramInstance, ObjectValue);    var watch1 = new Stopwatch();    watch1.Start();    for (var i = 0; i < Times; i++)    {        action(ProgramInstance, ObjectValue);    }    watch1.Stop();    Console.WriteLine(watch1.Elapsed + " (Dynamic Set ObjectProperty)");}

结果如下：

Test Set Value：00:00:00.0003237 (Directly Set IntProperty)00:00:00.3160570 (Reflection Set IntProperty)00:00:00.0132668 (Dynamic Set IntProperty)-----00:00:00.0028183 (Directly Set ObjectProperty)00:00:00.2937783 (Reflection Set ObjectProperty)00:00:00.0150118 (Dynamic Set ObjectProperty)

虽然跟直接赋值不能比，但比反射快大概30倍。

全部代码,希望对大家有帮助.