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Understanding Constant Data

Now that you can create fields that can be modified using type properties, allow me to illustrate how

to define data that can never change after the initial assignment. C# offers the const keyword to

define constant data. As you might guess, this can be helpful when you are defining a set of known

values for use in your applications that are logically connected to a given class or structure.

Turning away from the Employee example for a moment, assume you are building a utility class

named MyMathClass that needs to define a value for the value PI (which we will assume to be 3.14).

Begin by creating a new Console Application project named ConstData. Given that we would not

want to allow other developers to change this value in code, PI could be modeled with the following

constant:

namespace ConstData

{

class MyMathClass

{

public const double PI = 3.14;

}

class Program

{

static void Main(string[] args)

{

Console.WriteLine("***** Fun with Const *****\n");

Console.WriteLine("The value of PI is: {0}", MyMathClass.PI);