Enumerations - Illustrated C# 2005 - page 302

Suppose, for example, that you have used the enum declaration for CardDeckSettings
(given in the preceding code), and have not used the Flags attribute. The first line of the follow-
ing code creates a variable (named ops ) of the enum type, and sets the value of a single flag bit.
The second line uses ToString to get the string name of the member represented by that value.
CardDeckSettings ops = CardDeckSettings.SingleDeck; // Set the bit flag.
Console.WriteLine( ops.ToString() ); // Print its name.
This code produces the following output:
SingleDeck
Suppose, however, that you set two bit flags instead of one, as in the following code:
// Set two bit flags.
ops = CardDeckSettings.SingleDeck | CardDeckSettings.Animation;
Console.WriteLine( ops.ToString() ); // Print what?
The resulting value of ops is 9, where 1 is from the SingleDeck flag, and 8 is from the
Animation flag. In the second line, when ToString attempts to look up the value in the list of
enum members, it finds that there is no member with the value 9—so it just returns the string
representing 9. The resulting output is the following:
9
If, however, you use the Flags attribute before the declaration of the enum, that tells the
ToString method that the bits can be considered separately. In looking up the value, it would
find that 9 corresponds to the two bit flag members SingleDeck and Animation . It would then
return the string containing their names, separated by a comma and space, as shown here:
SingleDeck, Animation