C# 0 The Complete Reference

static

 class called 

NumericFn

 to hold a set of 

static

 methods 

that operate on a numeric value. Because all of the members of 

NumericFn

 are declared 

static

,

the class can also be declared 

static

, which prevents it from being instantiated. Thus, 

NumericFn

serves an organization role, providing a good way to logically group related methods.

// Demonstrate a static class.

using System;

static class NumericFn {

  // Return the reciprocal of a value.

  static public double Reciprocal(double num) {

    return 1/num;

  }

  // Return the fractional part of a value.

  static public double FracPart(double num) {

    return num - (int) num;

  }

  // Return true if num is even.

  static public bool IsEven(double num) {

    return (num % 2) == 0 ? true : false;

  }

  // Return true if num is odd.

  static public bool IsOdd(double num) {

    return !IsEven(num);

  }

}

class StaticClassDemo {

  static void Main() {

    Console.WriteLine("Reciprocal of 5 is " +

                      NumericFn.Reciprocal(5.0));

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    Console.WriteLine("Fractional part of 4.234 is " +

                      NumericFn.FracPart(4.234));

    if(NumericFn.IsEven(10))

      Console.WriteLine("10 is even.");

    if(NumericFn.IsOdd(5))

      Console.WriteLine("5 is odd.");

    // The following attempt to create an instance of

    // NumericFn will cause an error.

//  NumericFn ob = new NumericFn(); // Wrong!

  }

}

The output from the program is shown here.

Reciprocal of 5 is 0.2

Fractional part of 4.234 is 0.234

10 is even.

5 is odd.

Notice that the last line in the program is commented-out. Because