C# Enum

Enumeration types

The enum keyword is used to declare an enumeration, a distinct type that consists of a set of named constants called the enumerator list.

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public static class GenericStatus
{
   public enum GenStatusEnum
   {
      Pending,
      Approved,
      Declined
   }

   public static string ReadStatus(int id)
   {
      GenStatus s;
      Enum.TryParse<GenStatus>(id.ToString(), out s);
      return s.ToString();
   }
}

Enumeration types as bit flags

You can use an enumeration type to define bit flags

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using System;

namespace EnumDemo.Enum
{
    [Flags]
    public enum Days
    {
        None = 0,
        Sunday = 1,
        Monday = 2,
        Tuesday = 4,
        Wednesday = 8,
        Thursday = 16,
        Friday = 32,
        Saturday = 64
    }
}

You create a bit flags enum by applying the System.FlagsAttribute attribute and defining the values appropriately so that AND, OR, NOT and XOR bitwise operations can be performed on them.

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using EnumDemo.Enum;
using System;

namespace EnumDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // Initialize with two flags using bitwise OR.
            var meetingDays = Days.Tuesday | Days.Thursday | Days.Friday;
            Console.WriteLine($"Meeting days are {meetingDays} with flag value {(int)meetingDays}");
            // Meeting days are Tuesday, Thursday, Friday with flag value 52

            // Toggle a flag using bitwise XOR, this will remove `Days.Tuesday` from `meetingDays`
            meetingDays = meetingDays ^ Days.Tuesday;
            Console.WriteLine($"Meeting days are {meetingDays} with flag value {(int)meetingDays}");
            // Meeting days are Thursday, Friday with flag value 48

            // Test value of flags using bitwise AND, this is checking for the existance of `Days.Thursday` in `meetingDays`
            bool test = (meetingDays & Days.Thursday) == Days.Thursday;
            Console.WriteLine($"Thursday {(test == true ? "is" : "is not")} a meeting day.");
            // Thursday is a meeting day.
        }
    }
}