Class Modifiers and their uses in C# .Net

Class Modifiers and their uses in C# .Net
Filed under: Computer Science — Tags: Basic Programming, C#.Net, OOP — sadi02 @ 6:56 am

Class/Interface (Base class)
Inheritance (Inherited class)

Implementation (Interface)

(Child)
(Instance)

Is initiated??

General
Abstract
Sealed
Static*

General
Yes
Yes
Yes
No
No
Yes

Abstract
Yes
Yes
Yes
No
No
No

Sealed
No
No
No
No
No
Yes

Static
No
No
No
No
No
No

Interface
Yes
Yes
Yes
No
Yes
No





















This table is for showing relationship between a base class and child class

In this table I want to show the accessibility among the various types of classes and interface. From this table you also can know what type of class can be initiated. This is one example that helps you to understand the table.

If you use Abstract class as base class and take a general class as child and want to inherit, this will possible …here you can see..

Base: Abstract (ASadi)

Child: Interface (Sadi)

Accessibility: Yes

abstract class Sadi : ASadi

{

#region ASadi Members

public int getint() {

throw new Exception(“The method or operation is not implemented.”); }

#endregion

}

If you execute this code, it executes properly

From the first column of the table we can say that general class inherites both general and abstract class and also implements an interface. Theses classes can not inherites sealed as well as static class. only General and Sealed classes can be initiated.

From the table and above disscussion we can conclude that,

Abstract Class

A class defined as abstract is used as a base class. Such a class is used for the purpose of inheritance only i.e. other classes are derived from this class. We cannot create an object of an abstract class.An abstract class may contain methods and properties. The classes derived from the abstract class inherit these methods and properties. The abstract class may also contain abstract methods and properties. Abstract method and properties do not have any functionality. The derived class defines their full functionality.

Here is an example of an abstract class:

abstract class MyAbstract { public abstract void AbMethod(); }

Sealed Class

Classes can be declared as sealed. This is accomplished by putting the sealed keyword before the keyword class in the class definition. For example:

public sealed class classSealed { // Class members here. public string ID; public double Price; } A sealed class cannot be used as a base class. For this reason, it cannot also be an abstract class. Sealed classes are primarily used to prevent derivation. Because they can never be used as a base class, some run-time optimizations can make calling sealed class members slightly faster. Sealing a class means one can not derive from it. Sealing a method means one can not override it. In C# structs are implicitly sealed; therefore, they cannot be inherited. If we try to inherit from a sealed class in another class we will get compile time error about Inconsistent accessibility (code is shown in following code listing). In C# a method can not be declared as sealed. However when we override a method in a derived class, we can declare the overridden method as sealed as shown below. By declaring it as sealed, we can avoid further overriding of this method.

Static Class


Static classes are classes that contain only static members. Following is an example of static class. public static MyClass { …..}

A class defined as abstract is used as a base class. Such a class is used for the purpose of inheritance only i.e. other classes are derived from this class. We cannot create an object of an abstract class.An abstract class may contain methods and properties. The classes derived from the abstract class inherit these methods and properties. The abstract class may also contain abstract methods and properties. Abstract method and properties do not have any functionality. The derived class defines their full functionality.

Here is an example of an abstract class:

abstract class MyAbstract { public abstract void AbMethod(); }