比较对象在.net中

问题描述

这是任何不同于CLR的角度来看，以实施的IEqualityComparer VS覆盖 == 运营商的财产，你在将使用的IEqualityComparer＆LT; T＆GT; ？如果是这样，当你使用一个对其他？

Is it any different from the CLR standpoint to implement IEqualityComparer vs overriding the == operator for the property you would use in the IEqualityComparer<T>? And if so, when would you use one against the other?

修改

确定它有一定道理所使用的哈希表的实现中IEqaulityComparer - 它溜出了我的脑海，当我张贴的问题。那么，关于IEnumerable的的LINQ的的扩展。这是否意味着执行这些类型的扩展方法时.NET建立了一个哈希表？

Ok it does make sense that the IEqaulityComparer used by the implementations of Hashtable - it slipped out of my mind when I was posting the question. So what about the extensions of Linq of IEnumerable. Does that mean that .net builds up a Hashtable when executing those kind of extension methods?

推荐答案

的IEqualityComparer 不是等于，等于为为对象（例如方法），​​但EqualityComparer是在LINQ的装饰，比如你想要做具体的不同的：

IEqualityComparer is not equal, equal is for object (instance method) but EqualityComparer is for decoration for example in linq you want do specific distinct:

personList.OrderBy（P =＆GT; p.ID）.Distinct（新MyEqualityComparer（））

和

  class MyEqualityComparer: IEqualityComparer<Person>
  {

    public bool Equals(Person p1, Person p2)
    {
       if (p1.Age == p2.Age)
          return true;
       return false;
    }


    public int GetHashCode(Person p)
    {
        return p.Id.GetHashCode();
    }

  }

但平等是人：

but equal is for Person:

public class Person
{
 public int ID{get;set;}
 public int Age{get;set;}
 public override bool Equals(object o)
 {
   //do stuff
 }
}

您可以通过的IEqualityComparer做任何数量的装饰，但你不能用实例方法做到这一点（你可以写personList.Distinct（新AnotherComparer），...）

you can do any number of decoration by IEqualityComparer but you can't do this by instance method (you can write personList.Distinct(new AnotherComparer) ,...)

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