The Enum Keyword and Its Functional Usage

Introduction

The 'enum' Keyword is of Value Type. It is used to define integral constant and literals. It is inherited from the base class library(BCL) - 'Enum' where Enum's static methods are used by enum type for parsing enum values. This article tries to cover some of the enum functionality through code demonstration. Below is the source code which highlights various enum methods that are useful during the development phase.

Source Code

using System;
using System.Collections.Generic;
using System.Text;

namespace EnumSample
{
    class Program
    {
        public class EnumExamples
        {
            //Enum can also be derived from datatype-
            //Type byte, sbyte, short, ushort, int, uint, long, or ulong 
            public enum Status : byte
            { 
                REPORTED,
                OPEN,
                VERIFIED,
                CLOSED,
                REOPEN                
            }

            //Enum having Character Literal values
            public enum Colour 
            {
                RED='R',
                YELLOW='Y'                
            }

            //Enum having Numeric values
            public enum NumberType
            {
                WHOLE=0,
                NATURAl=1,
                EVEN=2,
                ODD=3
            }

            //MSDN --Example
            //http://msdn.microsoft.com/en-us/library/sbbt4032(VS.80).aspx
            [Flags]
            public enum CarOptions
            {
                SunRoof = 0x01,
                Spoiler = 0x02,
                FogLights = 0x04,
                TintedWindows = 0x08,
            }
            //END--

        }
        static void Main(string[] args)
        {
            //************************ENUM VALUES*******************************
            Console.WriteLine
                ("Output Enum Byte Value  : {0}",(byte)EnumExamples.Status.REPORTED);
            //Output Enum Byte Value  : 0
            Console.WriteLine("Output Enum Character Literal Value : 
                        {0}", (char)EnumExamples.Colour.RED);
            //Output Enum Character Literal Value : R
            Console.WriteLine("Output Enum Integer Value : {0}", 
                        (int)EnumExamples.NumberType.NATURAl);
            //Output Enum Integer Value : 1


            //************************ENUM NAMES*********************************
            Console.WriteLine("Output Enum Name as String Datatype : {0}",
                               EnumExamples.Status.REPORTED.ToString());
            //Output Enum Name as String Datatype :REPORTED
            Console.WriteLine("Output Enum Name as String Datatype : {0}",
                               EnumExamples.Colour.RED.ToString());
            //Output Enum Name as String Datatype :RED
            Console.WriteLine("Output Enum Name as String Datatype : {0}",
                               EnumExamples.NumberType.NATURAl.ToString());
            //Output Enum Name as String Datatype :NATURAL

            //****Enum.Parse--Input Parameter (typeof(enum),string)******
            Console.WriteLine("Output Enum.Parse Return As Typeof(Enum)
                               With IgnoreCase=False: {0}",
                               (EnumExamples.Status)Enum.Parse(typeof
                               (EnumExamples.Status), "REPORTED"));
            //Output Enum.Parse Return As Typeof(Enum) With 
              IgnoreCase=False: REPORTED
            Console.WriteLine("Output Enum.Parse Return As Typeof(Enum) 
                               With IgnoreCase=True: {0}", 
                               (EnumExamples.Status)Enum.Parse(typeof
                               (EnumExamples.Status), "reported", true));
            //Output Enum.Parse Return As Typeof(Enum) With 
              IgnoreCase=True: REPORTED

            //*****Enum.GetName--Input Parameter (typeof(enum),integer)*****
            Console.WriteLine("Output Enum.Parse Return As Typeof(Enum) :
                     {0}", Enum.GetName(typeof(EnumExamples.Status), 2));
            //Output Enum.Parse Return As Typeof(Enum) :VERIFIED
            
            
            //***Enum.ToObject --Input Parameter Can Be (Integer)|
              (Literal Constant)**
            Console.WriteLine("Output Enum.ToObject Return As Typeof(Enum) :
                     {0}", Enum.ToObject(typeof(EnumExamples.Colour), 'R'));
            //Output Enum.Parse Return As Typeof(Enum) :RED

            //******Enum.Format*********
            Console.WriteLine("Output Enum.Format Return As Typeof(Enum) :
                            {0}", Enum.Format(typeof(EnumExamples.Colour), 
                             EnumExamples.Colour.RED, "x"));
            //Output Enum.Format Return As Typeof(Enum) :00000052
            Console.WriteLine("Output Enum.Format Return As Typeof(Enum) : 
                              {0}", Enum.Format(typeof(EnumExamples.Colour),
                               EnumExamples.Colour.RED, "d"));
            //Output Enum.Format Return As Typeof(Enum) :82

            //****Enum.GetUnderlyingType *******
            Console.WriteLine("Output Enum.GetUnderlyingType Return Typeof
                               (Enum) : {0}", Enum.GetUnderlyingType(typeof
                               (EnumExamples.Colour)));
            //Output Enum.Format Return As Typeof(Enum) :System.Int32

            //****Enum.IsDefined-Input Parameter(Interger Only)for 'R'=82****
            Console.WriteLine("Output Enum.IsDefined Return as bool indicates
                    constant in the enum exist or not. : {0}", Enum.IsDefined
                   (typeof(EnumExamples.Colour), 82));
            //Output Enum.IsDefined Return as bool indicates constant in the
              enum exist or not.:82


            /*Enum.Names - To Load DropdownList--(TEXT)
             * Note that if one tries to load enum names into dropdownlist, one should
             * take note that enum only supports one word (no space).
            */
            int enumCounter = Enum.GetNames(typeof
             (EnumExamples.NumberType)).Length;                        
            foreach (string strName in Enum.GetNames(typeof
                   (EnumExamples.NumberType)))
            {
                Console.WriteLine("Enum for byte {0}: {1}", Enum.GetNames
          (typeof(EnumExamples.NumberType)).Length - enumCounter, strName);
                enumCounter--;
            }

            //Enum.Names - To Load DropdownList--(VALUE)
            int enumCounter1 = Enum.GetValues(typeof(EnumExamples.NumberType)).Length;
            foreach (int iValues in Enum.GetValues(typeof(EnumExamples.NumberType)))
            {
                Console.WriteLine("Enum for byte {0}: {1}", 
              Enum.GetValues
                  (typeof(EnumExamples.NumberType)).Length - enumCounter1, iValues);
                enumCounter1--;
            }
           
            //MSDN Example
            //http://msdn.microsoft.com/en-us/library/sbbt4032(VS.80).aspx
            EnumExamples.CarOptions options = EnumExamples.CarOptions.SunRoof
            | EnumExamples.CarOptions.FogLights;
            Console.WriteLine(options);
            Console.WriteLine((int)options);
            /* Output:
                SunRoof, FogLights
                5
            */
            /*
             * Notice that if you remove FlagsAttribute, 
             * the example will output the following:
             * 5
             * 5 
            */
            //END MSDN
            Console.Read();          
        }
    }
}

Feedback

I have tried to incorporate all the possible examples of enum which can be useful during development. Any suggestions or ideas about the functional usage of 'enum' will add more value to our learnings.

History

• 16^th May, 2008: Initial post

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)