c# - 根据基类的 Equals() 使派生类相等

Question

我有两个类，它们都派生自同一个父类:

public class People{
    public string BetterFoot;

    public override bool Equals(object obj){
        if (obj == null || this.GetType() != obj.GetType())
            return false;
        People o = (People)obj;
        return (this.BetterFoot == o.BetterFoot);
    }

public class LeftiesOrRighties: People{
    public string BetterHand;

    public override bool Equals(object obj){
        if (obj == null || this.GetType() != obj.GetType())
            return false;
        LeftiesOrRighties o = (LeftiesOrRighties)obj;
        return (this.BetterFoot == o.BetterFoot) &&
        (this.BetterHand == o.BetterHand)
    }
}

public class Ambidextrous: People{
    public string FavoriteHand;
}

(那里也有 GetHashCodes，但我知道它们可以工作。) 我想根据它们的根 Equals() 来比较它们的集合:

ThoseOneHanded = new List<LeftiesOrRighties>(){new LeftiesOrRighties(){BetterFoot = "L"}};
ThoseTwoHanded = new List<Ambidextrous>(){new Ambidextrous(){BetterFoot = "L"}};
//using NUnit
Assert.That ((People)ThoseOneHanded[0], Is.EqualTo((People)ThoseTwoHanded[0])));

不幸的是，这会返回false。

为什么？难道类型转换不应该使它们(出于所有意图和目的，即使不完全相同)具有相同的类型，从而使用基本方法吗？如果不是，我如何真正将底层类型转换回 People？

Answer 1

Cast 不会更改对象本身，因此 GetType 的结果将始终相同，因此您的 this.GetType() != obj.GetType() 将为 true，因此函数将返回 false。

以下逻辑可能会获得您想要的行为(并且您不需要强制转换为 People)

public class People 
{ 
    public string BetterFoot; 

    public override bool Equals(object obj)
    { 
        var o = obj as People;
        if (o == null) return false;
        return (this.BetterFoot = o.BetterFoot); 
} 

public class LeftiesOrRighties: People 
{ 
    public string BetterHand; 

    public override bool Equals(object obj) 
    { 
        var o = obj as LeftiesOrRighties; 
        if ( o == null) return base.Equals(obj);
        return (this.BetterFoot = o.BetterFoot) && (this.BetterHand = o.BetterHand) 
    } 
} 

public class Ambidextrous: People
{ 
    public string FavoriteHand; 
}