Declaring constants in C#.NET

In this article we will see a small example of using constants in c#. constants are declared with a keyword const .

> The program below is to find the area and perimeter of circle in which we use const . 
> In the program below we have declared PI as a constant whose value is given as 3.14 
   It means PI value cannot be changed either at compile time or run-time .

> Any Integral or string variables can be declared as constants.
   We can also declare constants as public to use it in all the classes in a program.

using System;

namespace Constants

{

    class Program

    {

        static void Main(string[] args)

        {

            //declaring const variable PI

            const double PI = 3.14;

            Console.WriteLine("*** www.ProgrammingPosts.blogspot.com ***");

            Console.WriteLine(">>> c# Program to find Area and Perimeter of Circle <<< \n");

            Console.Write("Enter radius value: ");

            int r = Convert.ToInt32(Console.ReadLine()); //taking radius as input

            double area = PI * r * r; //getting area of circle

            Console.WriteLine("Are of circle is: " + area);

 

            //if we try to assign a value to PI , we get compile-time error

            //PI = 123;

            double perimeter = 2 * PI * r; //getting perimeter of circle

            Console.WriteLine("Perimeter of circle: " + perimeter);

          

            Console.Read();

        }

    }

}

Sample Output :