C# Simplified - Classes
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Classes are the fundamental concept in an Object Oriented Programming Language such as C#. It would be more appropriate to discuss the meaning of a class with reference to an object. This is because these two words are interrelated. While a class is a combination of related objects, an object is an instance of the respective class. Actually, .NET Framework itself provides us with lot of classes with which you can perform a wide variety of tasks. But before applying these classes in a C# program, you have to define your own class. It is defined as shown below:
Listing 1.7
class Computer
{
// Declarations goes here
}
The opening and closing curly braces are important while declaring a class. It is in between these braces you declare variables, Main() method and also perform lot of other tasks.
Creating an instance of a class
After declaring a class you can create an instance of it by using the new keyword. The general syntax for creating an instance of a class is shown below:
Listing 1.8
YourClassname Yourobjectname = new Constructor();
Hence, for a class named Computer the declaration should be as in listing 1.9
Listing 1.9
Computer comp = new Computer();
To access a variable using the above object name, you should use the dot operator as shown in listing 1.10:
Listing 1.10
using System;
class VarAccess
{
int x = 1000;
int y = 2000;
public static void Main()
{
VarAccess va = new VarAccess();
Console.WriteLine(va.x);
Console.WriteLine(va.y);
}
}
In the above listing, the variables x and y are declared outside the Main() method. Hence, they are called as Instance variables. You need to create an object only for accessing an Instance variable. As soon as you create a variable, .NET allocates memory and it is immediately destroyed after the execution of the program with the help of the built-in garbage collector.
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