C Sharp Constant

Constants:

Constant is variable of a class of which the value remain fixed.They are declared without using static keyword. we can use a constant in the class in which it is defined, referring to it by name.  we can also use the constant in other classes, prefixing the name of the constant with the class name.  it's mandatory to assign a value to it. By default a constant is static and we cannot change the value of a constant variable throughout the entire program. Constants can be of any of the basic data types like an integer constant, a floating constant, a character constant, or a string literal.

Defining Constants

Constants are defined using the const keyword. Syntax for defining a constant is:

const <data_type> <constant_name> = value;

Ex.

    const double Pi = 3.14159;

    const double Rvalue = 1.8766;

    const string Name = "Suhail Osmani";

We cannot include the static keyword when declaring a constant.  A constant by default static, so the static keyword would be  will generate an error if you use  before it.

/ This is Correct

const string Remarks = "Exellent";

// This is incorrect

static const int Age = 42;

Defining Contant inside Class : We can define a constant within a class that contains related data and methods or a class,  containing a collection of constants.

public class contants

{   

    Public const double Pi = 3.14159;

    Public const double Rvalue = 1.8766;

    Public const string Name = "Suhail Osmani";

}

Initialization of a Constant

`

A constant must be initialized at time of decalaration . Otherwise, it will give  an error like "A const field requires a value to be provided

// This is Correct

    const string Remarks = "Exellent";

// This is incorrect

    const string Remarks;

Using  Constant in Program: Let us use a constant in a program to clarify a constant

using System;

namespace DeclaringConstants

{

    class Program

    {

        static void Main(string[] args)

        {

            const double pi = 3.14159;   

            // constant declaration 

            double r;

            Console.WriteLine("Enter Radius of Circle: ");

            r = Convert.ToDouble(Console.ReadLine());

            double Circle_Circumfrence = 2 * pi * r;

 Console.WriteLine("Radius: {0}, Circumfrence: {1}", r, Circle_Circumfrence);

            Console.ReadLine();

        }

    }

}

Output:

Enter Radius: 

3

Radius: 3, Circumfrence: 18.84954