如何检查是否设置了多个枚举标志？ [英] How do I check if more than one enum flag is set?

问题描述

我只想知道是否设置了一个枚举标志，而不是哪一个。我目前的想法是检查它是否是2的幂。有没有更好的方式内置枚举类型？

I just want to know if exactly one enum flag is set, not which ones. My current thinking is to check if it is a power of 2. Is there a better way built into enum types?

[Flags]
enum Foo
{
Flag1 = 0x01,
Flag2 = 0x02,
Flag3 = 0x04,
Flag4 = 0x08,
Flag5 = 0x10,
Flag6 = 0x20,
Flag7 = 0x40,
Flag8 = 0x80
}

private bool ExactlynOneFlagSet(Foo myFoo)
{
  var x = (byte) myFoo;
  return (x != 0) && ((x & (x - 1)) == 0); //Check if a power of 2
}

if(!ExactlynOneFlagSet(Foo myFoo))
{
   //Do something
}

推荐答案

它的一个位操作！

if ((myFoo & (myFoo -1)) != 0) //has more than 1 flag

该语句检查 myFoo 的值是否不是电源的两个。或者反之亦然，语句（myFoo&（myFoo -1））== 0 检查两个的权力。这个想法是，只有单个标志值才是两个。设置多个标志将导致两个值 myFoo 的无功。

The statement checks if the value of myFoo is not power of two. Or, vice versa, the statement (myFoo & (myFoo -1)) == 0 checks for power of two. The idea is that only single flag values will be power of two. Setting more than one flag will result in a non power of two value of myFoo.

可以找到更多信息在这个答案中有类似的问题： https://stackoverflow.com/a/1662162/2404788 。

More information can be found in this answer to a similar question: https://stackoverflow.com/a/1662162/2404788.

有关位操作的更多信息，请访问 http：// en .wikipedia.org / wiki / Bitwise_operation

For more information about bit operations go to http://en.wikipedia.org/wiki/Bitwise_operation

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