Abstract Class In C#

C# Abstract Class

 

An abstract class is an incomplete class or special class we can't be instantiated. The purpose of an abstract class is to provide a blueprint for derived classes and set some rules what the derived classes must implement when they inherit an abstract class.

 

We can use an abstract class as a base class and all derived classes must implement abstract definitions. An abstract method must be implemented in all non-abstract classes using the override keyword. After overriding the abstract method is in the non-Abstract class. We can derive this class in another class and again we can override the same abstract method with it.

 

C# Abstract Class Features

1. An abstract class can inherit from a class and one or more interfaces.
2. An abstract class can implement code with non-Abstract methods.
3. An Abstract class can have modifiers for methods, properties etc.
4. An Abstract class can have constants and fields.
5. An abstract class can implement a property.
6. An abstract class can have constructors or destructors.
7. An abstract class cannot be inherited from by structures.
8. An abstract class cannot support multiple inheritance.

Example 1

#region

//An abstract calss can inherit from a class and one or more interfaces.

interface IVendorTransDetails
{
    void getVendorID();
}
interface IClaimsTracker
{
    void getSeqID();
}
class ClaimsMaster
{
    string getDCNNO()
    {
        return "PC20100308A00005";
    }
}

Example 2

abstract class Abstract : ClaimsMaster, IClaimsTracker, IVendorTransDetails
{
    //Here we should implement modifiers oterwise it throws complie-time error
    public void getVendorID()
    {
        int s = new int();
        s = 001;
        Console.Write(s);
    }

    public void getSeqID()
    {
        int SeqID = new int();
        SeqID = 001;
        Console.Write(SeqID);
    }
}
#endregion

Example 3

    #region

    //An abstract class can implement code with non-Abstract methods.

abstract class NonAbstractMethod
{
    //It is a Non-abstract method we should implement code into the non-abstract method on the class.
    public string getDcn()
    {
        return "PS20100301A0012";
    }
    public abstract void getSeqID();
}
class Utilize : NonAbstractMethod
{
    public override void getSeqID()
    {
    }

}
#endregion

Example 4

#region
//Abstract class can have modifiers for methods,properties and An abstract class can implement a property

public abstract class abstractModifier
{
    private int id;
    public int ID
    {
        get { return id; }
        set { id = value; }
    }
    internal abstract void Add();
}
#endregion

Example 5

#region
//Abstract class can have constant and fields
public abstract class ConstantFields
{
    public int no;
    private const int id = 10;
}
#endregion

Example 6

#region
//An abstract class can have constructors or destructors
abstract class ConsDes
{
    ConsDes()
    {
    }
    ~ConsDes()
    {
    }
}
#endregion

Example 7

#region
//An abstract class cannot be inherited from by structures
public struct test
{
}
//We can't inheritance the struct class on the abstract class
abstract class NotInheritanceStruct
{
}
#endregion

Example 8

#region
//An abstract class cannot support multiple inheritance
class A
{
}
class B : A
{
}
abstract class Container : B //But we can't iherit like this : A,B
{
}
#endregion

Conclusion

 

In this article I have given some simple examples of how to use abstract classes in C#. 

 

Here is a detailed article on Abstract Classes In C#. 

 

Here is another related reading: Method Overloading and Overriding In C#