C# 在标志上使用按位运算符
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Using Bitwise operators on flags
提问by Malfist
I have four flags
我有四个标志
Current = 0x1
Past = 0x2
Future = 0x4
All = 0x7
Say I receive the two flags Past and Future (setFlags(PAST | FUTURE)). How can I tell if Pastis in it? Likewise how can I tell that Currentis not in it? That way I don't have to test for every possible combination.
假设我收到两个标志 Past 和 Future ( setFlags(PAST | FUTURE))。我怎么知道它Past是否在里面？同样，我怎么能说那Current不在里面呢？这样我就不必测试每种可能的组合。
采纳答案by Marc Gravell
If you want all bits in the test mask to match:
如果您希望测试掩码中的所有位都匹配：
if((value & mask) == mask) {...}
If you want any single bit in the test mask to match:
如果您希望测试掩码中的任何单个位匹配：
if((value & mask) != 0) {...}
The difference is most apparent when you are testing a value for multiple things.
当您测试多个事物的值时，差异最为明显。
To test for exclusion:
要测试排除：
if ((value & mask) == 0) { }
回答by Peter
you could use AND on it and check if the result is the same as you and with?
你可以在上面使用 AND 并检查结果是否与你和 with 相同？
回答by Misko
if ((flags & PAST) == PAST)
{
// PAST is there
}
if ((flags & CURRENT) != CURRENT)
{
// CURRENT is not there
}
回答by Samantha Branham
(value & Current) == Current
回答by Vilx-
First of all - use enums with FlagAttribute. That's what it's for.
首先 - 将枚举与 FlagAttribute 一起使用。这就是它的用途。
[Flags]
public enum Time
{
None = 0
Current = 1,
Past = 2,
Future = 4
All = 7
}
Testing then is done like this:
然后测试是这样完成的：
if ( (x & Time.Past) != 0 )
Or this:
或这个：
if ( (x & Time.Past) == Time.Past )
The latter will work better if "Past" was a combination of flags and you wanted to test them all.
如果“过去”是标志的组合并且您想对它们全部进行测试，则后者会更好地工作。
Setting is like this:
设置是这样的：
x |= Time.Past;
Unsetting is like this:
取消设置是这样的：
x &= ~Time.Past;
回答by Brian Rasmussen
You may also want to add an extension methodlike this
您可能还需要添加一个扩展方法是这样
enum states {
Current = 0x1,
Past = 0x2,
Future = 0x4,
All = 0x7
};
static bool Is(this states current, states value) {
return (current & value) == value;
}
then you can do:
那么你可以这样做：
if(state.Is(states.Past)) {
// Past
}
回答by Kody
An addendum to Marc Gravell and Vilx-'s answer:
Marc Gravell 和 Vilx- 的回答的附录：
Your flagged enum shouldn't specify the amount for "All", it should just include your existing values. This goes for any calculated values.
您标记的枚举不应指定“全部”的数量，它应该只包括您现有的值。这适用于任何计算值。
[Flags]
public enum Time
{
None = 0,
Current = 1,
Past = 2,
Future = 4,
All = Current | Past | Future
}
Note that Vilx- removed the use of Hexadecimal for values. This is important because once you're past 0x8, your values will have to comply with Hex. You should just stay in decimal.
请注意，Vilx- 删除了对值使用十六进制。这很重要，因为一旦超过 0x8，您的值就必须符合十六进制。你应该只保留十进制。
EDIT:I also want to add that you can use bit shifting rather than hex/decimal.
编辑：我还想补充一点，您可以使用位移位而不是十六进制/十进制。
This looks like:
这看起来像：
[Flags]
public enum Time
{
None = 0,
Current = 1,
Past = 1 << 1, // 2, 10 binary
Future = 1 << 2, // 4, 100 binary
All = Current | Past | Future
}
回答by Ogglas
If you use .NET 4 or later I prefer to do this, cleaner imao:
如果您使用 .NET 4 或更高版本，我更喜欢这样做，更干净的 imao：
[Flags]
public enum Time
{
None = 0
Current = 1,
Past = 2,
Future = 4
}
myProp = Time.Past | Time.Future;
if (myProp.HasFlag(Time.Past))
{
// Past is set...
}
