Understanding the Flag Enums in C#

Flags Enum Attribute

1. Use the [Flags] attribute to represent the enum as a bit field.
2. The [Flags] attribute should be used whenever the enumerable represents a collection of possible values, rather than a single value. Such collections are often used with bitwise operators.

   [Flags]
   public enum SignalColor
   {
       None = 0,//0000
       Red = 1,//0001
       Green = 2,//0010
       Yellow = 4,//0100
       Stop = Red | Yellow//0101
   }
   public class FlagsEnum
   {
       public static void Test()
       {
           //SignalColor.Stop & SignalColor.Red == SignalColor.Red
           if (SignalColor.Stop.HasFlag(SignalColor.Red))
           {
               Console.WriteLine("Red is to stop");
           }
       }
   }

Explanation of the above code

1. The value of SignalColor.Stop is 0101 in binary (which is 5 in decimal).
2. The value of SignalColor.Red is 0001 in binary (which is 1 in decimal).

When you perform a bitwise AND operation between SignalColor.Stop (0101) and SignalColor.Red (0001), the result is.

• 0101 (Stop)
• 0001 (Red)

Result

0001 (which equals SignalColor.Red)

Summary

The SignalColor enum uses the [Flags] attribute to represent a combination of signal colors using bitwise operations.