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[ C# ] 判断一个类是否实现了某个接口的多种方法及性能分析

IEntity为一个接口，Entity为实现IEntity接口的类：

interface IEntity {  int Id { get; set; } } public class Entity : IEntity {  public int Id { get; set; }  public string Prop { get; set; } }

我们要判断Entity是否实现了IEntity接口，根据找到的帖子

c# 如何判断一个类是否实现了某个接口

在C#中判断某个类是否实现了某个接口

整理有如下五种方式：

Entity entity = new Entity();

if (entity is IEntity)

{

}

Entity entity = new Entity();

IEntity temp = entity as IEntity;

if (temp != null)

{

}

if (typeof(IEntity).IsAssignableFrom(typeof(Entity)))

{

}

if (typeof(Entity).GetInterfaces().Contains(typeof(IEntity)))

{

}

if (typeof(Entity).GetInterface("IEntity")!=null)

{

}

但是我们知道，前2种方式要实例化Entity的新实例，后面三种方式要用到反射，这都是相对耗性能的操作！

那么这几种判断Entity是否实现了IEntity接口的方式哪一种相对来说对性能的消耗低呢？

我们让每个方法都执行1000万次：（以下测试均为Release 模式，.net framework 4.5.1框架）

Stopwatch stopwatch = null; int count = 10000000; Console.WriteLine("执行次数 {0}", count); stopwatch = Stopwatch.StartNew(); for (int i = 0; i < count; i++) {  Entity entity = new Entity();  if (entity is IEntity) { } } Console.WriteLine(stopwatch.Elapsed); stopwatch = Stopwatch.StartNew(); for (int i = 0; i < count; i++) {  Entity entity = new Entity();  IEntity temp = entity as IEntity;  if (temp != null) { } } Console.WriteLine(stopwatch.Elapsed); stopwatch = Stopwatch.StartNew(); for (int i = 0; i < count; i++) {  if (typeof(IEntity).IsAssignableFrom(typeof(Entity))) { } } Console.WriteLine(stopwatch.Elapsed); stopwatch = Stopwatch.StartNew(); for (int i = 0; i < count; i++) {  if (typeof(Entity).GetInterfaces().Contains(typeof(IEntity))) { } } Console.WriteLine(stopwatch.Elapsed); stopwatch = Stopwatch.StartNew(); for (int i = 0; i < count; i++) {  if (typeof(Entity).GetInterface("IEntity")!=null) { } } Console.WriteLine(stopwatch.Elapsed);

测试结果：

[ C# ] 判断一个类是否实现了某个接口的多种方法及性能分析