8abstact class in c#
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The document discusses the differences between abstract classes and interfaces in C#. Abstract classes can contain both abstract and non-abstract methods while interfaces contain only abstract methods. Abstract classes are used to provide common functionality for derived classes, while interfaces define a contract that classes implement. The document provides examples of abstract classes and interfaces in C# code, demonstrating how derived classes must implement abstract methods from the base class or interface.
8abstact class in c#
- 1. C# Tutorial Part 8: Abstract Class vs Interface www.sirykt.blogspot.com
- 2. • Abstract classes are the way to achieve abstraction in C#. Abstraction in C# is the process to hide the internal details and showing functionality only. • Abstraction can be achieved by two ways: • Abstract class • Abstract class and interface both can have abstract methods which are necessary for abstraction. • Abstract Method: • A method which is declared abstract and has no body is called abstract method. It can be declared inside the abstract class only. Its implementation must be provided by derived classes. • For example:public abstract void draw(); • An abstract method in C# is internally a virtual method so it can be overridden by the derived class. You can't use static and virtual modifiers in abstract method declaration. • C# Abstract class • In C#, abstract class is a class which is declared abstract. It can have abstract and non- abstract methods. It cannot be instantiated. Its implementation must be provided by derived classes. Here, derived class is forced to provide the implementation of all the abstract methods. • Let's see an example of abstract class in C# which has one abstract method draw(). Its
- 3. • Let's see an example of abstract class in C# which has one abstract method draw(). Its implementation is provided by derived classes: Rectangle and Circle. Both classes have different implementation. • using System; • public abstract class Shape • { public abstract void draw(); } • public class Rectangle : Shape • { public override void draw() • { Console.WriteLine("drawing rectangle..."); • } } • public class Circle : Shape • { public override void draw() • { Console.WriteLine("drawing circle..."); } } • public class TestAbstract • { public static void Main() • { Shape s; • s = new Rectangle(); • s.draw(); • s = new Circle(); • s.draw(); } } • Output: • drawing ractangle... drawing circle...
- 4. • C# Interface • Interface in C# is a blueprint of a class. It is like abstract class because all the methods which are declared inside the interface are abstract methods. It cannot have method body and cannot be instantiated. • It is used to achieve multiple inheritance which can't be achieved by class. It is used to achieve fully abstraction because it cannot have method body. • Its implementation must be provided by class or struct. The class or struct which implements the interface, must provide the implementation of all the methods declared inside the interface. • Note: • Interface methods are public and abstract by default. You cannot explicitly use public and abstract keywords for an interface method.Interfaces define properties, methods, and events, which are the members of the interface. Interfaces contain only the declaration of the members. • It is the responsibility of the deriving class to define the members. Interfaces are declared using the interface keyword. It is similar to abstract class declaration. Interface statements are public by default
- 5. Fully abstract class(interface) • interface: it maintains only method declarations • syntax: • interface iname • {void esal(); • void tsal(); } • Interface are similar to abstract classes. • Interfaces contains only methods without body. These interfaces are called fully abstract classes. • Interfaces supports a structure like multiple inheritance. Interfaces cannot be instantiated .
- 6. • Let's see the example of interface in C# which has draw() method. Its implementation is provided by two classes: Rectangle and Circle. • using System; • public interface Drawable • { void draw(); } • public class Rectangle : Drawable • { public void draw() • { Console.WriteLine("drawing rectangle..."); • } } • public class Circle : Drawable • { public void draw() • { Console.WriteLine("drawing circle..."); • } } • public class TestInterface • { public static void Main() • { Drawable d; • d = new Rectangle(); • d.draw(); • d = new Circle(); • d.draw(); } } • Output: • drawing ractangle... drawing circle...
- 7. • Note: • Interfaces define properties, methods, and events, which are the members of the interface. • Interfaces contain only the declaration of the members. It is the responsibility of the deriving class to define the members. • Interfaces are declared using the interface keyword. It is similar to abstract class declaration. • Interface statements are public by default
- 8. • Sealed class : • Which class gives the full functionality that classes are called sealed classes. sealed class there is no child class. • Sealed is a keyword. sealed class restricts the inheritance. sealed classes having instance variable. Sealed methods are not overidable • Note: • Sealed classes are used to restrict the inheritance feature of object oriented programming. Once a class is defined as a sealed class, the class cannot be inherited • example on sealed class: • using System; • namespace interfaceexample • { sealed class emp • { int sal, bonus, ta, ts;}}
- 9. Feature Interface Abstract class Multiple inheritance A class may inherit several interfaces. A class may inherit only one abstract class. Default implementation An interface cannot provide any code, just the signature. An abstract class can provide complete, default code and/or just the details that have to be overridden. Access Modfiers An interface cannot have access modifiers for the subs, functions, properties etc everything is assumed as public An abstract class can contain access modifiers for the subs, functions, properties Core VS Peripheral Interfaces are used to define the peripheral abilities of a class. In other words both Human and Vehicle can inherit from a IMovable interface. An abstract class defines the core identity of a class and there it is used for objects of the same type. Homogeneity If various implementations only share method signatures then it is better to use Interfaces. If various implementations are of the same kind and use common behaviour or status then abstract class is better to use. Speed Requires more time to find the actual method in the corresponding classes. Fast Adding functionality (Versioning) If we add a new method to an Interface then we have to track down all the implementations of the interface and define implementation for the new method. If we add a new method to an abstract class then we have the option of providing default implementation and therefore all the existing code might work properly. Fields and An abstract class can have fields and constrants
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