C# Flag Charlie-Fox

Question

Hi everybody. I've been trying to emulate in C# a behavior which I was implementing without any problems in C++. I have a flag collection, which based on powers of 2, and a flag which I need to check if it exists in the collection.

  byte flagCollection = 1 | 2 | 4 | 8;
  byte flag = 2;

  if ((flagCollection & flag) != 0) MessageBox.Show("y"); else MessageBox.Show("n");

Now, the problem is that whatever I set Flag to (2, 3, 100, 211), I always get "y", except for 0. Of course, 1, 2, 4, 8 would be some constants which have various meanings in my application.

In C++:

if (flagCollection & flag)

Would result in TRUE for the variables above.

Answer 1

well, if you're flag collection has OR'd 1,2,4,8, uh yes I think every positive integer that's not a multiple of 16 when &'d to it is going to return something. Or am I missing something?

Answer 2

The way you are doing it seems correct. I'm not really sure what behavior you are expecting. Any of the flags you listed (2, 3, 100, 211) do contain an element of 1 | 2 | 4 | 8. If you want to check whether all of them are present you should be doing

if ((flagCollection & flag) == flag) 
   // ...

Answer 3

Would this work?

[Flag]
public enum flagCollection {
  Type1,
  Type2,
  Type4,
  Type8,
}

flagCollection testValue = flagCollection.Type2

if ((testValue & flagCollection.Type2) == flagCollection.Type2) {
   MessageBox.Show("y");
} else {
   MessageBox.Show("n");
}

Not in front of the compiler so cant chek if that will work or not.