Class 创建性能大比拼（反射，泛型反射，泛型创建，缓存Emit，非缓存Emit）
一说到反射，很多人都想到了性能，更有甚者直接说“慎用反射，遗患无穷”，“用反射，感觉怎么像是退步啊～”，看到这种言论，直接把反射妖魔化了，如果这种言论长此以往，势必会对很多对反射初学者造成负面影响。反射是一把双刃剑，看你怎样使用了，下面我就用代码说话。
class TestEntity { }
1. 手工创建TestEntity
[TestInfo(Category = "Class.Constructor", Name = "Direct")]
class DirectInvokeMode:IRunable
{
public void Run()
{
new TestEntity();
}
}
2. 反射创建TestEntity
[TestInfo(Category = "Class.Constructor", Name = "Reflect")]
class ReflectInvokeMode : IRunable
{
public void Run()
{
Activator.CreateInstance(typeof(TestEntity));
}
}
3. 泛型反射创建TestEntity
[TestInfo(Category = "Class.Constructor", Name = "GenericReflect")]
class GenericReflectInvokeMode : IRunable
{
public void Run()
{
Activator.CreateInstance<TestEntity>();
}
}
4. Generic 直接创建
[TestInfo(Category = "Class.Constructor", Name = "Generic Create")]
class GenericCreateInvokeMode : IRunable
{
public void Run()
{
Create<TestEntity>();
}
static T Create<T>() where T : new()
{
return new T();
}
}
[TestInfo(Category = "Class.Constructor", Name = "Emit")]
class EmitInvokeMode : IRunable
{
static readonly ConstructorHandler Ctor = typeof(TestEntity).GetConstructor(Type.EmptyTypes).GetCreator();
public void Run()
{
Ctor();
}
}
6. 不缓存Emit的创建
[TestInfo(Category = "Class.Constructor", Name = "NoCacheEmit")]
class NoCacheEmitInvokeMode : IRunable
{
public void Run()
{
typeof(TestEntity).GetConstructor(Type.EmptyTypes).GetCreator()();
}
}
测试程序：（经过5次比较执行10次创建Class对象）
for (int i = 0; i < 5; i++)
{
foreach (var item in Mappers)
CodeTimer.Time(item.Metadata.Category + "->" + item.Metadata.Name, 100000, () => item.Value.Run());
}
输出结果：
------ Test started: Assembly: NLite.Test.dll ------
Class.Constructor->Direct
Time Elapsed: 7ms
CPU Cycles: 156,250
Gen 0: 0
Gen 1: 0
Gen 2: 0
Class.Constructor->Reflect
Time Elapsed: 328ms
CPU Cycles: 2,968,750
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->GenericReflect
Time Elapsed: 143ms
CPU Cycles: 1,406,250
Gen 0: 1
Gen 1: 1
Gen 2: 0
Class.Constructor->Generic Create
Time Elapsed: 147ms
CPU Cycles: 1,562,500
Gen 0: 1
Gen 1: 1
Gen 2: 0
Class.Constructor->Emit
Time Elapsed: 7ms
CPU Cycles: 0
Gen 0: 2
Gen 1: 1
Gen 2: 0
Class.Constructor->NoCacheEmit
Time Elapsed: 12,534ms
CPU Cycles: 120,781,250
Gen 0: 162
Gen 1: 81
Gen 2: 0
Class.Constructor->Direct
Time Elapsed: 5ms
CPU Cycles: 0
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Reflect
Time Elapsed: 320ms
CPU Cycles: 2,968,750
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->GenericReflect
Time Elapsed: 147ms
CPU Cycles: 1,250,000
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Generic Create
Time Elapsed: 159ms
CPU Cycles: 1,406,250
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Emit
Time Elapsed: 6ms
CPU Cycles: 0
Gen 0: 2
Gen 1: 0
Gen 2: 0
Class.Constructor->NoCacheEmit
Time Elapsed: 12,786ms
CPU Cycles: 119,218,750
Gen 0: 162
Gen 1: 81
Gen 2: 0
Class.Constructor->Direct
Time Elapsed: 6ms
CPU Cycles: 156,250
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Reflect
Time Elapsed: 325ms
CPU Cycles: 3,125,000
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->GenericReflect
Time Elapsed: 145ms
CPU Cycles: 1,406,250
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Generic Create
Time Elapsed: 148ms
CPU Cycles: 1,406,250
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Emit
Time Elapsed: 12ms
CPU Cycles: 0
Gen 0: 2
Gen 1: 0
Gen 2: 0
Class.Constructor->NoCacheEmit
Time Elapsed: 12,658ms
CPU Cycles: 121,093,750
Gen 0: 163
Gen 1: 81
Gen 2: 0
Class.Constructor->Direct
Time Elapsed: 6ms
CPU Cycles: 0
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Reflect
Time Elapsed: 334ms
CPU Cycles: 3,125,000
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->GenericReflect
Time Elapsed: 149ms
CPU Cycles: 1,718,750
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Generic Create
Time Elapsed: 147ms
CPU Cycles: 1,250,000
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Emit
Time Elapsed: 6ms
CPU Cycles: 156,250
Gen 0: 2
Gen 1: 0
Gen 2: 0
Class.Constructor->NoCacheEmit
Time Elapsed: 12,771ms
CPU Cycles: 122,187,500
Gen 0: 162
Gen 1: 81
Gen 2: 0
Class.Constructor->Direct
Time Elapsed: 6ms
CPU Cycles: 0
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Reflect
Time Elapsed: 326ms
CPU Cycles: 3,437,500
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->GenericReflect
Time Elapsed: 148ms
CPU Cycles: 1,562,500
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Generic Create
Time Elapsed: 157ms
CPU Cycles: 1,406,250
Gen 0: 1
Gen 1: 0
Gen 2: 0
Class.Constructor->Emit
Time Elapsed: 6ms
CPU Cycles: 0
Gen 0: 2
Gen 1: 0
Gen 2: 0
Class.Constructor->NoCacheEmit
Time Elapsed: 12,573ms
CPU Cycles: 122,187,500
Gen 0: 162
Gen 1: 81
Gen 2: 0
1 passed, 0 failed, 0 skipped, took 67.77 seconds (NUnit 2.5.5).
性能比较结果应该是一目了然了！
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