利用表达式树构建委托改善反射性能
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：
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：
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：
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
/// <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
The End。
===重要更新===
我把上面的方法用在项目中才发现陷入了一个悖论。就是往往需要使用反射的上下文中是没有实例类型的，而有了实例类型的上下文中有往往不需要反射。所以构建表达式树是需要去掉实例的类型参数，在表达式树中做类型转换，这样会有一点点的性能损失，但同时又带来一个好处，使用时类型参数少了一个，写起来方便了一点。两个主要代码如下：
/// <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(typeof(object), "instance");
//((T)instance)
var castExpression = Expression.Convert(instanceExpression, methodInfo.ReflectedType);
//((T)instance).Call(params)
callExpression = Expression.Call(castExpression, methodInfo, paramExpressions);
paramExpressions.Insert(0, instanceExpression);
}
var lambdaExpression = Expression.Lambda(callExpression, paramExpressions);
return lambdaExpression.Compile();
}
//使用
public static Action<object> BuildAction(MethodInfo methodInfo)
{
return (Action<object>)BuildDynamicDelegate(methodInfo);
}
public static Action<object, T1> BuildAction<T1>(MethodInfo methodInfo)
{
return (Action<object, T1>)BuildDynamicDelegate(methodInfo);
}
/// <summary>
/// 动态构造赋值委托
/// </summary>
/// <typeparam name="TProperty">属性类型</typeparam>
/// <param name="propertyInfo">属性元数据</param>
/// <returns>强类型委托</returns>
public static Action<object, TProperty> BuildSetPropertyAction<TProperty>(PropertyInfo propertyInfo)
{
var instanceParam = Expression.Parameter(typeof(object), "instance");
var valueParam = Expression.Parameter(typeof(TProperty), "value");
//((T)instance)
var castExpression = Expression.Convert(instanceParam, propertyInfo.ReflectedType);
//((T)instance).Property
var propertyProperty = Expression.Property(castExpression, propertyInfo);
//((T)instance).Property = value
var assignExpression = Expression.Assign(propertyProperty, valueParam);
var lambdaExpression = Expression.Lambda<Action<object, TProperty>>(assignExpression, instanceParam, valueParam);
return lambdaExpression.Compile();
}
//使用
var action = BuildSetPropertyAction<int>(IntPropertyInfo);
action(ProgramInstance, IntValue);
