C# 0 The Complete Reference

Pass References to Methods

Up to this point, the examples in this book have been using value types, such as 

int

 or 

double

, as parameters to methods. However, it is both correct and common to use a 

reference type as a parameter. Doing so allows an object to be passed to a method. For 

example, consider the following program:

// References can be passed to methods.

using System;

class MyClass {

  int alpha, beta;

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  public MyClass(int i, int j) {

    alpha = i;

    beta = j;

  }

  // Return true if ob contains the same values as the invoking object.

  public bool SameAs(MyClass ob) {

    if((ob.alpha == alpha) & (ob.beta == beta))

       return true;

    else return false;

  }

  // Make a copy of ob.

  public void Copy(MyClass ob) {

    alpha = ob.alpha;

    beta  = ob.beta;

  }

  public void Show() {

    Console.WriteLine("alpha: {0}, beta: {1}",

                      alpha, beta);

  }

}

class PassOb {

  static void Main() {

    MyClass ob1 = new MyClass(4, 5);

    MyClass ob2 = new MyClass(6, 7);

    Console.Write("ob1: ");

    ob1.Show();

    Console.Write("ob2: ");

    ob2.Show();

    if(ob1.SameAs(ob2))

      Console.WriteLine("ob1 and ob2 have the same values.");

    else

      Console.WriteLine("ob1 and ob2 have different values.");

    Console.WriteLine();

    // Now, make ob1 a copy of ob2.

    ob1.Copy(ob2);

    Console.Write("ob1 after copy: ");

    ob1.Show();

    if(ob1.SameAs(ob2))

      Console.WriteLine("ob1 and ob2 have the same values.");

    else

      Console.WriteLine("ob1 and ob2 have different values.");

  }

}

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This program generates the following output:

ob1: alpha: 4, beta: 5

ob2: alpha: 6, beta: 7

ob1 and ob2 have different values.

ob1 after copy: alpha: 6, beta: 7

ob1 and ob2 have the same values.

The