Question

我已经完成了question

我理解，有必要实施==，!=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);
    }
}

我认为，我已正确编写代码以覆盖==，!=，Equals运算符。虽然，我得到编译错误如下。

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

所以，问题是 - 如何覆盖上面的运算符＆amp;摆脱这个错误？

Answer 1

正如Selman22所说，您将覆盖默认的object.Equals方法，该方法接受object obj而不是安全的编译时类型。

为了实现这一点，请使用类型工具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.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 == obj2);
    }

    public bool Equals(Box other)
    {
        if (ReferenceEquals(null, other))
        {
            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)
    {
        if (ReferenceEquals(null, obj))
        {
            return false;
        }
        if (ReferenceEquals(this, obj))
        {
            return true;
        }

        return obj.GetType() == GetType() && Equals((Box)obj);
    }

    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，您使用相等运算符进行浮点比较，您可能会遇到精度损失。

Answer 2

我认为你宣布Equals方法是这样的：

public override bool Equals(BOX obj)

由于object.Equals方法接受一个对象，因此没有方法可以使用此签名覆盖。你必须像这样覆盖它：

public override bool Equals(object obj)

如果您想要类型安全的Equals,，则可以实施IEquatable<BOX>。

Answer 3

事实上，这是一个＆＃34;如何＆＃34;学科。所以，这是参考实现：

    public class BOX
    {
        double height, length, breadth;

        public static bool operator == (BOX b1, BOX b2)
        {
            if (null == b1)
                return (null == b2);

            return b1.Equals(b2);
        }

        public static bool operator != (BOX b1, BOX b2)
        {
            return !(b1 == b2);
        }

        public override bool Equals(object obj)
        {
            if (obj == null || GetType() != obj.GetType())
                return false;

            var b2 = (BOX)obj;
            return (length == b2.length && breadth == b2.breadth && height == b2.height);
        }

        public override int GetHashCode()
        {
            return height.GetHashCode() ^ length.GetHashCode() ^ breadth.GetHashCode();
        }
    }

参考：https://msdn.microsoft.com/en-us/library/336aedhh(v=vs.100).aspx#Examples

Answer 4

public class BOX
{
    double height, length, breadth;

    public static bool operator == (BOX b1, BOX b2)
    {
        if (b1 is null)
            return b2 is null;

        return b1.Equals(b2);
    }

    public static bool operator != (BOX b1, BOX b2)
    {
        return !(b1 == b2);
    }

    public override bool Equals(object obj)
    {
        if (obj == null)
            return false;

        return obj is BOX b2? (length == b2.length && 
                               breadth == b2.breadth && 
                               height == b2.height): false;

    }

    public override int GetHashCode()
    {
        return (height,length,breadth).GetHashCode();
    }
}

运算符重载==，！=，等于

4 个答案: