c# - "is"关键字和 Equals 方法的覆盖

Question

documentation for the keyword "is"指出:

The is operator only considers reference conversions, boxing conversions, and unboxing conversions. Other conversions, such as user-defined conversions, are not considered.

这在实践中意味着什么？用它来检查结构是否是某种类型是错误的吗？例如，

public struct Point2D
{
    public int X;
    public int Y;

    ...

    public override bool Equals(Object value)
    {
        if (value != null && value is Point2D)   // or if (value != null && GetType() == value.GetType())
        {
            Point2D right = (Point2D)value;
            return (X == right.X && Y == right.Y);
        }
        else return false;
    }

    ...
}

Answer 1

检查一个结构是否是某种类型是可以的。该文档表示用户定义的 explicit和 implicit在考虑给定对象是否属于指定类型时，不会评估转换运算符，即使存在可以将其转换为所述类型的用户定义运算符也是如此。