C# 0 The Complete Reference

PART I

C h a p t e r   6 :  

I n t r o d u c i n g   C l a s s e s   a n d   O b j e c t s  

135

PART IPART I

    this.Width = w;

    this.Height = h;

  }

  public int Area() {

    return this.Width * this.Height;

  }

}

class UseRect {

  static void Main() {

    Rect r1 = new Rect(4, 5);

    Rect r2 = new Rect(7, 9);

    Console.WriteLine("Area of r1: " + r1.Area());

    Console.WriteLine("Area of r2: " + r2.Area());

  }

}

Actually, no C# programmer would use 

this

 as just shown because nothing is gained 

and the standard form is easier. However, 

this

 has some important uses. For example, the 

C# syntax permits the name of a parameter or a local variable to be the same as the name of 

an instance variable. When this happens, the local name 

hides

 the instance variable. You can 

gain access to the hidden instance variable by referring to it through 

this

. For example, the 

following is a syntactically valid way to write the 

Rect( )

 constructor:

public Rect(int Width, int Height) {

  this.Width = Width;

  this.Height = Height;

}

In this version, the names of the parameters are the same as the names of the instance 

variables, thus hiding them. However, 

this

 is used to “uncover” the instance variables.

www.freepdf-books.com

---

This page intentionally left blank 

www.freepdf-books.com

---

7

Arrays and Strings

T

his chapter returns to the subject of C#’s data types. It discusses arrays and the