Question

鉴于课程如下，

public class Number
{
  public int X { get; set; }
  public int Y { get; set; }
}

如何定义重载运算符==以便我可以使用以下语句：

Number n1 = new Number { X = 10, Y = 10 };
Number n2 = new Number { X = 100, Y = 100 };

if (n1 == n2)
    Console.WriteLine("equal");
else
    Console.WriteLine("not-equal");

//根据以下评论更新//

这是另一个问题：在我看来，C＃的运算符重载与C ++不同。在C ++中，此重载运算符在目标类之外定义为独立函数。在C＃中，这个重载函数实际上已嵌入到目标类中。

有人可以就这个话题给我一些评论吗？

谢谢

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication3
{
    public class Number
    {
        public int X { get; set; }
        public int Y { get; set; }

        public Number() { }
        public Number(int x, int y)
        {
            X = x;
            Y = y;
        }

        public static bool operator==(Number a, Number b)
        {
            return ((a.X == b.X) && (a.Y == b.Y));
        }

        public static bool operator !=(Number a, Number b)
        {
            return !(a == b);
        }

        public override string ToString()
        {
            return string.Format("X: {0}; Y: {1}", X, Y);
        }

        public override bool Equals(object obj)
        {
            var objectToCompare = obj as Number;
            if ( objectToCompare == null )
                return false;

            return this.ToString() == obj.ToString();
        }

        public override int GetHashCode()
        {
            return this.ToString().GetHashCode();
        }

    }

    class Program
    {
        static void Main(string[] arg)
        {
            Number n1 = new Number { X = 10, Y = 10 };
            Number n2 = new Number { X = 10, Y = 10 };

            if (n1 == n2)
                Console.WriteLine("equal");
            else
                Console.WriteLine("not-equal");

            Console.ReadLine();
        }
    }
}

Answer 1

public static bool operator ==(YourClassType a, YourClassType b)
{
    // do the comparison
}

更多信息here。简而言之：

任何重载operator ==的类型也应该重载运算符！=
任何超载operator ==的类型也应该覆盖 Equals
建议任何覆盖Equals的类也会覆盖 GetHashCode

Answer 2

来自MSDN Docs：

public static bool operator ==(ThreeDPoint a, ThreeDPoint b)
{
    // If both are null, or both are same instance, return true.
    if (System.Object.ReferenceEquals(a, b))
    {
        return true;
    }

    // If one is null, but not both, return false.
    if (((object)a == null) || ((object)b == null))
    {
        return false;
    }

    // Return true if the fields match:
    return a.x == b.x && a.y == b.y && a.z == b.z;
}

public static bool operator !=(ThreeDPoint a, ThreeDPoint b)
{
    return !(a == b);
}

Answer 3

以下是如何执行此操作的简短示例，但我强烈建议阅读Guidelines for Overloading Equals() and Operator == (C# Programming Guide)以了解Equals（）和==等之间的交互。

public class Number
{
  public int X { get; set; }
  public int Y { get; set; }

  public static bool operator ==(Number  a, Number b)
  {
    // TODO
  }
}

Answer 4

自己过载操作员：

public static bool operator ==(Number a, Number b)
{
    // do stuff
    return true/false;
}

如何定义operator ==

4 个答案: