c# - ReferenceEquals() 的合法使用

Question

在按照声明式风格编写的 .NET 程序中，ReferenceEquals() 有哪些合法用途？

Answer 1

不确定“按照声明式编写”是什么意思，但是 ReferenceEquals 通常在覆盖 == 运算符时使用。来自 http://msdn.microsoft.com/en-us/library/ms173147.aspx :

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;
}

请务必查看下面的注意以了解理由:

Note: A common error in overloads of operator == is to use (a == b), (a == null), or (b == null) to check for reference equality. This instead creates a call to the overloaded operator ==, causing an infinite loop. Use ReferenceEquals or cast the type to Object, to avoid the loop.