Test that only a single bit is set in Flags Enum [duplicate]

问题

This question already has answers here:

How do I check if more than one enum flag is set? (5 answers)

Closed 18 days ago.

So I have a flags Enum

public Enum test
{
   test1 = 1,
   test2 = 2,
   test3 = 4,
   etc.
}

How can I test that one bit, and only one bit is set?

I've 100% done this before but my mind is not working this am!

回答1:

To check that only a single bit is set in a number, the number must (by definition) be a power of two. As such, you can use the following to test:

int intVal = ((int)myEnumFlags);
bool singleBitIsSet = intVal != 0 && (intVal & (intVal-1)) == 0;

My favorite reference for this kind of thing:

http://aggregate.org/MAGIC

来源：https://stackoverflow.com/questions/19376748/test-that-only-a-single-bit-is-set-in-flags-enum