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Abstract Class in C#

By Annathurai Subbaiah on March 09, 2010
An Abstract class is an incomplete class or special class we can't instantiate.
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An Abstract class is an incomplete class or special class we can't instantiate. We can use an Abstract class as a Base Class. An Abstract method must be implemented in the non-Abstract class 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.

Features:

  1. An abstract calss 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 to understand abstract classes. I am expecting feedback about this article.

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