Difference between constant and read-only in C#

                             Constant and readonly keywords in C# are used to maintain the value throughout the application without any change. But constant should be assigned a value at the time of declaration only, but there is no need to assigned value at the time of declaration of readonly variable, can be assigned a value in constructor. The following example shows below clarifies about the constant and readonly.

using System;

namespace CSHARP_Constant_ReadOnly

{

    class Program

    {

        static void Main(string[] args)

        {

            Abc abc = new Abc();

            abc.Display();

            Console.Read();

        }

    }

    class Abc

    {

        public const int a = 10;

        public readonly int b = 30;

        public readonly int c;

        public Abc()

            {

            b = 80;

            c = 90;

            }

       public void Display()

        {

            //If given values after initialization, then it throws the following errors

           // a = 50;  //The left-hand side of an assignment must be a variable, property or indexer

           // b = 20;   //A readonly field cannot be assigned to (except in a constructor or a variable initializer)

            Console.WriteLine(a);

            Console.WriteLine(b);

            Console.WriteLine(c);

        }

    }

}

Output :-