C# 中 is/not/or/and 的优先级

Question

模式匹配“不是”的优先顺序是什么？我意识到我写了一些这样的代码：

if (x is not TypeA or TypeB)

并隐含地假设我正在写：

if (!(x is TypeA) && !(x is TypeB))

但我刚刚意识到它可能被评估为：

if ((!x is TypeA) || (x is TypeB))

换句话说，“不”是否适用于“或分隔”列表，或者仅适用于列表中的下一个参数。我原来的声明是否需要写成这样：

if (x is not TypeA and not TypeB)

Answer 1

这是一个测试程序：

class A { }
class B : A { }
class C : A { }

A a1 = new A();
A a2 = new B();
A a3 = new C();

Console.WriteLine("A is not B or C " + (a1 is not B or C));
Console.WriteLine("B is not B or C " + (a2 is not B or C));
Console.WriteLine("C is not B or C " + (a3 is not B or C));

Console.WriteLine("A is not (B or C) " + (a1 is not (B or C)));
Console.WriteLine("B is not (B or C) " + (a2 is not (B or C)));
Console.WriteLine("C is not (B or C) " + (a3 is not (B or C)));

Console.WriteLine("A is not B and not C " + (a1 is not B and not C));
Console.WriteLine("B is not B and not C " + (a2 is not B and not C));
Console.WriteLine("C is not B and not C " + (a3 is not B and not C));

这是输出：

A is not B or C True
B is not B or C False
C is not B or C True

A is not (B or C) True
B is not (B or C) False
C is not (B or C) False

A is not B and not C True
B is not B and not C False
C is not B and not C False

因此“不是（B 或 C）”与“不是 B 且不是 C”相同。

但“不是 B 或 C”会检查它不是 B 或 C，这可能永远不是您想要做的事情。