如何在没有无限递归的情况下检查'=='运算符重载中的空值？

用途

ReferenceEquals

Foo foo1 = null;Foo foo2 = new Foo();Assert.IsFalse(foo1 == foo2);public static bool operator ==(Foo foo1, Foo foo2) {    if (object.ReferenceEquals(null, foo1))        return object.ReferenceEquals(null, foo2);    return foo1.Equals(foo2);}