C# const keyword Examples

The const keyword is used to create a constant field or constant local and cannot be reinitialized throughout the program. The const field or const local must be declared and initialized in one go. It is just a single statement which define constant. For example, public const double PI = 3.1415;

Example1 : Program with Error

using System;

namespace Console_const_keyword

{

    class Program

    {

        const double PI;// const field must be initialized when declared

        Pl = 3.1415; // a const field cannot be reinitialized post declaration

        static void Main(string[] args)

        {

            Console.WriteLine(PI);

        }

    }

}

Example2 : Program Corrected

using System;

namespace Console_const_keyword

{

    class Program

    {

        //constant field

        const double PI = 3.1415; // a const field cannot be reinitialized post declaration

        static void Main(string[] args)

        {

            //local variable

            double radius;

            //constant local

            const string local_const = "I am not a variable.";

            //local_const = "I cannot be reinitialized.";//error if uncommented

            radius = 100.50;

            Console.WriteLine(2*PI*radius);

            Console.WriteLine(local_const);

            //array size declaration

            const int myArraySize = 5;

            int[] myArray = new int[myArraySize];

            //initialize the array's values

            Random random = new Random();

            for (int i = 0; i < myArray.Length; i++)

            {

                myArray[i] = random.Next(10, 100);

                Console.WriteLine(myArray[i]);

            }

        }

    }

}

OUTPUT

631.4415

I am not a variable.

93

74

29

57

32

Example of use of const: We know that array is of fixed size and cannot be resized. To declare the size of an array we can use const.