c# - 运算符重载 ==, !=, Equals

Question

我已经完成了 question

我理解，有必要实现==、!= 和Equals()。

public class BOX
{
    double height, length, breadth;

    // this is first one '=='
    public static bool operator== (BOX obj1, BOX obj2)
    {
        return (obj1.length == obj2.length 
                    && obj1.breadth == obj2.breadth 
                    && obj1.height == obj2.height);
    }

    // this is second one '!='
    public static bool operator!= (BOX obj1, BOX obj2)
    {
        return !(obj1.length == obj2.length 
                    && obj1.breadth == obj2.breadth 
                    && obj1.height == obj2.height);
    }

    // this is third one 'Equals'
    public override bool Equals(BOX obj)
    {
        return (length == obj.length 
                    && breadth == obj.breadth 
                    && height == obj.height);
    }
}

我想，我已经正确地编写了代码来覆盖 ==,!=,Equals 运算符。虽然，我得到如下编译错误。

'myNameSpace.BOX.Equals(myNameSpace.BOX)' is marked as an override 
but no suitable method found to override.

因此，问题是 - 如何覆盖上述运算符并消除此错误？

Answer 1

正如 Selman22 所说，您正在覆盖默认值 object.Equals方法，它接受 object obj而不是安全的编译时类型。

为了实现这一点，让你的类型实现 IEquatable<Box> :

public class Box : IEquatable<Box>
{
    double height, length, breadth;

    public static bool operator ==(Box obj1, Box obj2)
    {
        if (ReferenceEquals(obj1, obj2)) 
            return true;
        if (ReferenceEquals(obj1, null)) 
            return false;
        if (ReferenceEquals(obj2, null))
            return false;
        return obj1.Equals(obj2);
    }
    public static bool operator !=(Box obj1, Box obj2) => !(obj1 == obj2);
    public bool Equals(Box other)
    {
        if (ReferenceEquals(other, null))
            return false;
        if (ReferenceEquals(this, other))
            return true;
        return height.Equals(other.height) 
               && length.Equals(other.length) 
               && breadth.Equals(other.breadth);
    }
    public override bool Equals(object obj) => Equals(obj as Box);

    public override int GetHashCode()
    {
        unchecked
        {
            int hashCode = height.GetHashCode();
            hashCode = (hashCode * 397) ^ length.GetHashCode();
            hashCode = (hashCode * 397) ^ breadth.GetHashCode();
            return hashCode;
        }
    }
}

另一件需要注意的事情是，您正在使用相等运算符进行浮点比较，您可能会遇到精度损失。