why we are not create object for abstract class

ramakotaiah patti

why we are not create object for abstract class ...so why we use this abstract class concept in real time c# programming and where we can use these abstract classes in realtime applications...

5 Replies

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Dilip Gupta9y ago
Reffer this link

http://csharp-video-tutorials.blogspot.in/2012/06/part-32-c-tutorial-abstract-classes.html
Mayank9y ago
Abstract classes are closely related to interfaces. They are classes that cannot be instantiated, and are frequently either partially implemented, or not at all implemented. One key difference between abstract classes and interfaces is that a class may implement an unlimited number of interfaces, but may inherit from only one abstract (or any other kind of) class. A class that is derived from an abstract class may still implement interfaces. Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed. They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code.
Fabio Silva Lima9y ago
Abstract classes are used for polymorphism to change some behavior.

Example:
public abstract class Animal{
public abstract string GetName();
}

public class Dog : Animal{

public override string GetName(){
  return "DOG";
}
}

public class Cat: Animal{
   public override string GetName(){
  return "CAT";
}
}

var animals = new List();
animals.Add(new Dog());
animals.Add(new Cat());
Dog and Cat are Animals. So you can create instances for any Animal you want to change a behavior for Animal.
Tapan Patel9y ago
abstract classes basically contains the definition or behavior that user wants to keep intact through out the application.
For example logging application trace to specific database.
Class absclass{
public void MakeDBConnection();
public void LogDataToSpecific (object objCon, obj Data)
   {
       //write data to passed connection object
   }
}
class yourclass: absclass
{
   public override void MakeDBConnection()
   {
        // make either MSSQL or mysql connection
   }

   public static void main(string[] args)
   {
    //
    yourclass obj = new yourclass();
    obj.LogDataToSpecific(connectionobj, data);
   }
}
Having such implementation makes easy for each derived class to make specific connection and there is no need to write custom method to write trace data to database as there is a method in abstract class that enforces unique behavior to write data to DB.
I hope this helps.
Nitin Sontakke9y ago
Let me try to explain the way I look at it.

One of the purposes of the abstract class is to club together the related functionality. For example, in pre-.NET days, there were several mathematical functions floating all over the language. There was no common place to find the function.

Because .NET went the object oriented way, it now has a class called Math. This class is abstract and contains the mathematical functions.

Now here is a simple question: The mathematics is a universal phenomenon. The add method which accepts two integers and returns an answer. What different functionality can you possibly add by creating an instance of the Math class?

This is not the case with the Customer class. There are several customers and each has it's own name, address, etc. For this reason, we need to create an instance of the class.

Hope you get the point.