4.Classed, Methods and Properties in C#.

Classed, Methods and Properties in C#.

A class is the fundamental topic to be discussed in any Object-Oriented Programming (OOP) language. A class is a combination of related objects whereas each object is an instance or a copy of the corresponding class. 

Lets use a figure to give you a clear idea about the two words called class and object.(Figure 1 - Structure of a Class)

Figure 1 - Structure of a Class

Telephone is a combination of Sony, Ericcson, Panasonic, and Siemens. Hence, Telephone is a class and the other four are its objects. Here, Compaq and HP can't be objects of the class Telephone. In C#, a class is a user-defined reference type. 

 We create an object out of the classes by using the "new" keyword and by applying the general syntax as shown in Listing 1:

Listing 1

Classname objectname = new Constructor();

To create an object for our class Telephone, you have to code as shown in Listing 2:

Listing 2

Telephone T= new Telephone();

To access any variable by using the above object name, we use the dot operator as shown in Listing 3:

Listing 3

using System;
class Access
{
  //Variables declared outside the main.
  int x = 100;
  int y = 200;
  public static void Main()
  {
    //Object created
    Access a = new Access();
 
    //Instance variables called
    Console.WriteLine(a.x);
    Console.WriteLine(a.y);
  }
}

In Listing 3, the variables are declared outside the main method. Hence, they are called Instance Variables. You have to create an object only for accessing an Instance variable. The additional memory created out of the object creation are automatically destroyed by the C# Garbage Collector.

Methods

Methods are blocks of code that perform some kind of action. There are two types of methods.

• Instance Method
• Static Method

 Instance Method

Instance Methods are methods declared outside the main method and can be accessed only by creating an object of the corresponding class.

using System;
class Instmethod
{
  //Method declared outside the main.
  void show()
  {
    int x = 100;
    int y = 200;
    Console.WriteLine(x);
    Console.WriteLine(y);
  }
 
  public static void Main()
  {
    //Object created
    Instmethod a = new Instmethod ();
 
    //Instance method called
    a.show();
  }

Declaring Methods with Parameters

You can declare methods with a variable name or names as a parameter. The complete code illustration is show below.

using System;
class Pmethod
{
  //Method declared with two parameters x and y of type integer
  void show(int x , int y)
  {
    Console.WriteLine(x);
    Console.WriteLine(y);
  }
 
  public static void Main()
  {
    //Object created
    Pmethod a = new Pmethod ();
 
    //Method called by passing two integer values
    a.show(200,250);
  }
}

Method Overloading

You can declare the signature of the same method once again in the same class but with different parameters. The parameters should be different. If not, the C# compiler would show errors. 

The complete code illustration is show below.

using System;
class Overloadmethod
{
 
  //Method declared with one integer parameter
  void show(int x)
  {
    Console.WriteLine(x);
  }
 
  //Method declared with two integer parameters
  void show(int a, int b)
  {
    Console.WriteLine(a);
    Console.WriteLine(b);
  }
 
  public static void Main()
  {
    //Object created
    Overloadmethod a = new Overloadmethod ();
 
    //Methods called by passing respective values
    a.show(100);
    a.show(300,500);
  }
}

Properties

Properties provide added functionality to the .NET Framework.

A C# property consists of:

• Field declaration
• Accessor Methods (getter and setter methods)

Getter methods are used to retrieve the field's value and setter methods are used to modify the field's value. C# uses a special Value keyword to achieve this. 

The sample code illustration is show below.

using System;
class Propertiesexample
{
 
  //Field "idValue" declared
  public string idValue;
 
  //Property declared
  public string IdValue
  {
 
    get
    {
      return idValue;
    }
    set
    {
      idValue = value;
    }
  }
 
  public static void Main(string[] args)
  {
 
    Propertiesexample pe = new Propertiesexample();
    pe.IdValue = "009878";
    string p = pe.IdValue;
    Console.WriteLine("The Value is {0}",p);
  }
}

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