C# Constant

In this chapter you will learn:

1. What is a constant
2. How to create a constant field
3. Example for defining a constant field
4. Local Constants

Description

A constant is a field whose value can never change.

These variables must be given initial values when they are declared. const implies static.

A constant can be any of the built-in numeric types, bool, char, string, or an enum type.

Syntax

We can create a public constant in the following way:

public class className
{ 
  public const type ConstantName = constant value; 
} 

Constants can be declared local to a method. For example:

static void Main() 
{ /*from  w  w w .j a  v a  2 s .c om*/
   const double twoPI  = 2 * System.Math.PI; 
   ... 
} 

Example

A constant is declared with the const keyword and must be initialized with a value. For example:

using System;//from   w w w. jav  a 2  s  .c o  m

class Constants
{
    public const int value1 = 33;
    public const string value2 = "Hello";
}
class MainClass
{
    public static void Main()
    {
        Console.WriteLine("{0} {1}", 
        Constants.value1, 
        Constants.value2);
    }
}

The code above generates the following result.

Example 2

const field can be used in a method.

The following code uses expressions to calculate and display the circumference of a circle.

class MainClass/*from  w  ww  .ja v  a  2  s.c  o m*/
{

  public static void Main()
  {

    const double Pi = 3.14159;
    double diameter = 2.5;

    double circumference = Pi * diameter;

    System.Console.WriteLine("Circumference = " + circumference);

  }

}

The code above generates the following result.

Next chapter...

What you will learn in the next chapter:

1. How to create read only field
2. Example for Read only field
3. How to set the initial value to a read only field in constructor

C# Constant