collections.Contains(T)方法

Question

我正在使用a System.Collections.Generic,其中包含我编写的类的实例.

我已经读过collections .Contains方法使用object.Equals(),或者Equals()从IEquatable接口中实现该方法.

我已经覆盖了对象方法,以及从界面实现.但是,Queue.Contains(instance)总是返回false.我究竟做错了什么？

例如...

class Foo : IEquatable<Foo>
{
    ...
    int fooField1;
    ...

    public override bool Equals(object obj)
    {
         Foo other = obj as Foo;
         bool isEqual = false;

         if (other.fooField1 == this.fooField1)
         { 
             isEqual = true;
         }

         return isEqual;         
    }

    public bool Equals(Foo other)
    {
         bool isEqual = false;

         if (other.fooField1 == this.fooField1)
         { 
             isEqual = true;
         }

         return isEqual;         
    }

}
...

void SomeFunction()
{
    Queue<Foo> Q = new Queue<Foo>();
    Foo fooInstance1 = new Foo();
    Foo fooInstance2 = new Foo();

    fooInstance1.fooField1 = 5;
    fooInstance2.fooField1 = 5;

    Q.Enqueue(fooInstanec1);
    if(Q.Contains(fooInstance2) == false)
    {
         Q.Enqueue(fooInstance2);
    }
}

fooInstance2始终添加到队列中.实际上,当我在调试器上运行它时,永远不会达到Equals的实现.

我究竟做错了什么？

Answer 1

一旦初始编译错误被整理出来,您的示例代码就会按预期工作.并不是它与提出的问题相关,请阅读重写等于(您还需要覆盖GetHashCode并检查错误情况,如null/type-mismatch).

class Foo : IEquatable<Foo>
    {
        private int _fooField1;
        public Foo(int value)
        {
            _fooField1 = value;
        }

        public override bool Equals(object obj)
        {
            return Equals(obj as Foo);
        }

        public bool Equals(Foo other)
        {
            return (other._fooField1 == this._fooField1);
        }
    }



    class Program
    {
        static void SomeFunction()
        {
            var Q = new Queue<Foo>();
            Foo fooInstance1 = new Foo(5);
            Foo fooInstance2 = new Foo(5);

            Q.Enqueue(fooInstance1);
            if (!Q.Contains(fooInstance2))
            {
                Q.Enqueue(fooInstance2);
            }
            else
            {
                Console.Out.WriteLine("Q already contains an equivalent instance ");
            }
        }

        static void Main(string[] args)
        {
            SomeFunction();
        }
    }