Abstract Function and Abstract Classes

Abstract Function: 

• A Function which contains only Declaration / Signature and doesn’t contain Implementation / Body / Definition, is known as Abstract function
• To make any function as abstract use abstract keyword
• An abstract function should be terminated
• Overriding of an abstract function is compulsory 

Abstract class:  

• A class which contains one (or) more direct functions is known as an abstract class
• To make any class as abstract use abstract keyword
• An abstract class can’t be instantiated directly
• It’s compulsory to create / derive a new class from an abstract class in order to provide functionality to its abstract functions
• An abstract class can contain non-abstract functions
• An abstract class can contain all members of a class
• By default abstract class functions are not treated as public and abstract

Example :-

Class Diagram:-

 

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace CAAbstract {     abstract class ClsEmployee     {         protected int EmpId, EAge;         protected string EName, EAddress;         public abstract void GetEmpData();         public virtual void DisplayEmpData()         {             Console.WriteLine("Employee Id is       :-  " + this.EmpId);             Console.WriteLine("Employee Name is     :-  " + this.EName);             Console.WriteLine("Employee Address is  :-  " + this.EAddress);             Console.WriteLine("Employee Age is      :-  " + this.EAge);         }     }     class ClsManager : ClsEmployee     {         double Bonus, CA;         public override void GetEmpData()         {             Console.Write("Enter Manager Details:- \n");             Console.WriteLine("Enter Manager id");             EmpId = Convert.ToInt32(Console.ReadLine());             Console.WriteLine("Enter Manager Name");             EName = Console.ReadLine();             Console.WriteLine("Enter Manager Bonus");             Bonus = Convert.ToDouble(Console.ReadLine());             Console.WriteLine("Enter Manager CA");             CA = Convert.ToDouble(Console.ReadLine());         }         public override void DisplayEmpData()         {             Console.WriteLine("Manager Id is    :-  " + EmpId);             Console.WriteLine("Manager Name is  :-  " + EName);             Console.WriteLine("Manager Bonus is :-  " + Bonus);             Console.WriteLine("Manager CA is    :-  " + CA);         }     }     class ClsAbstract     {         static void Main(string[] args)         {             ClsManager Obj1 = new ClsManager();             Obj1.GetEmpData();             Obj1.DisplayEmpData();             Console.Read();         }     } }

Output :-