Abstract class, derived class object in C#

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Hi,

I am having a abstract class 'AbsBase' having a method getDetails and there is derived class 'DerivedBase' which is implementing getDetails method of AbsBase as shown below......

C#

public abstract class AbsBase
{
   public abstract void getDetails();
} 

public class DerivedBase : AbsBase
{
   public override void getDetails()
     {
        //Implementation code
     }
}

C#

AbsBase obj =new DerivedBase();

so what is 'obj' here of 'AbsBase' or what we call to obj here....

What I have tried:

Abstract Class cannot be instantiate.......

Posted 24-Aug-20 0:38am

.NET- India

Updated 24-Aug-20 3:38am

Sandeep Mewara

v2

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PIEBALDconsult 24-Aug-20 11:00am

Are you saying that that code won't compile? It should.

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OriginalGriff · Answer 1 · 2020-08-24T00:54:00

Abstract classes can;t be instantiated, no - that's the whole point. They are a "generic base class" from which concrete examples are derived.
For example, a Car class would be abstract, and give rise to derived concrete classes FordFiesta1300, MercedesA180CDi, ToyotaHiLux, and so on - because you don't buy "a car", you buy "a Ford Fiesta 1300", or "a Mercedes A250e", or ...
Car describes all the thigs that make it "a car" : engine, steering wheel, drivers seat, four wheels, and so on; while MercedesA180CDi fills in the details: "2L Turbo Diesel", "W169 body shape", and so on. The actual instance of a car "my car" adds teh details which differenciate it from all other A180CDis: colour, VIN number, registration number, registered owner, current location, current speed, fuel in tank level, and so on.

In your example:

C#

AbsBase obj =new DerivedBase();

obj is of the type AbsBase, which means it can contain an instance of any class derived from AbsBase.
In Car terms:

C#

Car myCar = new MercedesA180CDi(Color.Black, "WDD169000J000000, "XX 99 XXX", originalGriff);

myCar can hold any type of Car - a ford, a Mercedes, a Citroen, ... because all such vehicles are derived from the abstract base class Car.

The system sorts out from the individual instance which method it shoudl call when you try to access a base class method:

C#

myCar.Drive();

Or

C#

obj.getDetails();

Make sense?