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。搜索一下，不难搜到老赵的这篇文章，下面是一些杂乱的笔记。（建议先看老赵的文章）
.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：
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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：
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00:00:00.0009710 (Directly invoke)00:00:00.4142893 (Reflection invoke)00:00:00.0194501 (Dynamic executor) |
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：
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00:00:00.0018801 (Directly invoke)00:00:02.4288876 (Reflection invoke)00:00:00.0141537 (Dynamic executor) |
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=""><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。
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/// <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：
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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：
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public void Call1(object o1, object o2, object o3) { }public void Call2(int o1, int o2, int o3) { } |
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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：
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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：
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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：
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var action = BuildSetPropertyAction<Program, object>(ObjectPropertyInfo);action(ProgramInstance, ObjectValue); |
来测试一下性能：
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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：
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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
The End。
http://www.cnblogs.com/lemontea/archive/2013/02/04/2891281.html
