C# in a Nutshell, Second Edition

Enums

               attributes? access-modifier?
new?
enum enum-name [ : integer-type ]?
{ [attributes? enum-member-name 
[ = value ]? ]* }

Enums specify a group of named numeric constants:

public enum Direction {North, East, West, South}

Unlike in C, enum members must be used with the enum type name. This resolves naming conflicts and makes code clearer:

Direction walls = Direction.East;

By default, enums are assigned integer constants 0, 1, 2, etc. You may optionally specify an alternative numeric type to base your enum on, and explicitly specify values for each enum member:

[Flags]
public enum Direction : byte {
   North=1, East=2, West=4, South=8
}
Direction walls = Direction.North | Direction.West;
if((walls & Direction.North) != 0)
    System.Console.WriteLine("Can't go north!");

The [Flags] attribute is optional, and informs the runtime that the values in the enum can be bit-combined, and should be decoded accordingly in the debugger or when outputting text to the console. For example:

Console.WriteLine(walls.Format( )); // Displays "North|West"
Console.WriteLine(walls); // Calls walls.ToString, displays "5"

The System.Enum type also provides many useful static methods for enums that allow one to determine the underlying type of an enum, to check if a specific value is supported, to initialize an enum from a string constant, to retrieve a list of the valid values, and other common operations such as conversions. Here is an example of the usage:

using System; public enum Toggle : byte { Off=0, On=1 } class ...