3.6 Enums

attributes? access-modifier?
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:

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 Test {
  static void Main( ) {
    Type t = Enum.GetUnderlyingType(typeof(Toggle));
    Console.WriteLine(t); // Prints "Byte"
    bool bDimmed = Enum.IsDefined(typeof(Toggle), "Dimmed");
    Console.WriteLine(bDimmed); // Prints "False"
    Toggle tog =(Toggle)Enum.Parse(typeof(Toggle), "On");
    Console.WriteLine(Enum.Format(typeof(Toggle), tog, "D")); // Prints "1"
    Console.WriteLine(tog); // Prints "On"
    object[ ] oa = Enum.GetValues(typeof(Toggle));
    foreach(Toggle toggle in oa) // Prints "On=1, Off=0"
      Console.WriteLine("{0}={1}", toggle,Enum.Format(typeof(Toggle), 
                                   toggle, "D")); 

3.6.1 Enum Operators

The operators relevant to enums are:

=  =   !=   <   >   <=   >=   +   -   ^  &  |   ~
=   +=   -=   ++  --   sizeof

3.6.2 Enum Conversions

Enums may be explicitly converted to other enums. Enums and numeric types may be explicitly converted to one another. A special case is the numeric literal 0, which may be implicitly converted to an enum.

    Part II: Programming with the .NET Framework
    Part IV: API Quick Reference