C# 枚举 - 根据掩码检查标志

Question

我有以下枚举标志:

[Flags]
private enum MemoryProtection: uint
{
    None             = 0x000,
    NoAccess         = 0x001,
    ReadOnly         = 0x002,
    ReadWrite        = 0x004,
    WriteCopy        = 0x008,
    Execute          = 0x010,
    ExecuteRead      = 0x020,
    ExecuteReadWrite = 0x040,
    ExecuteWriteCopy = 0x080,
    Guard            = 0x100,
    NoCache          = 0x200,
    WriteCombine     = 0x400,
    Readable         = (ReadOnly | ReadWrite | ExecuteRead | ExecuteReadWrite),
    Writable         = (ReadWrite | WriteCopy | ExecuteReadWrite | ExecuteWriteCopy)
}

现在我有一个枚举实例，我需要检查它是否可读。如果我使用以下代码:

myMemoryProtection.HasFlag(MemoryProtection.Readable)

在我的例子中它总是返回 false，因为我认为 HasFlag 检查它是否有每个标志。我需要一些优雅的东西来避免这样做:

myMemoryProtection.HasFlag(MemoryProtection.ReadOnly)         ||
myMemoryProtection.HasFlag(MemoryProtection.ReadWrite)        ||
myMemoryProtection.HasFlag(MemoryProtection.ExecuteRead)      ||
myMemoryProtection.HasFlag(MemoryProtection.ExecuteReadWrite)

我该怎么做？

Answer 1

您可以反过来检查条件，检查复合 enum 是否有标志，而不是检查复合的标志，如下所示:

if (MemoryProtection.Readable.HasFlag(myMemoryProtection)) {
    ...
}

这是一个例子:

MemoryProtection a = MemoryProtection.ExecuteRead;
if (MemoryProtection.Readable.HasFlag(a)) {
    Console.WriteLine("Readable");
}
if (MemoryProtection.Writable.HasFlag(a)) {
    Console.WriteLine("Writable");
}

这会打印Readable。