C# Tips of Inheritance and Instance of Class

Look at given below steps:

• If method in the base and derived class are same and not made virtual in the base class and not being override in the derived then following case will occur :
  
  1. using System;  
  2.   
  3. public class Program  
  4. {  
  5.    public static void Main()  
  6.    {  
  7.       Base objBase = new Base();  
  8.       objBase.Message(); // I amd Base  
  9.   
  10.       Derived objDerived = new Derived();  
  11.       objDerived.Message(); // I am Derived  
  12.   
  13.       // Now, set the reference of derived class to base class.  
  14.   
  15.       objBase = new Derived();  
  16.       objBase.Message(); // I am Base  
  17.   
  18.    }  
  19. }  
  20.   
  21.   
  22. public class Base  
  23. {  
  24.    public void Message()  
  25.    {  
  26.       Console.WriteLine("I am Base");  
  27.    }  
  28. }  
  29.   
  30. public class Derived : Base  
  31. {  
  32.    public void Message()  
  33.    {  
  34.       Console.WriteLine("I am Derived");  
  35.    }  
  36. }  
• Output:
  
  I am Base
  I am Derived
  I am Base
  
  Executing Code URL: .NET Fiddle.
  
  
• If method in the base and derived class are same and made virtual in the base class and being override in the derived then following case will occur:
  
  1. using System;   
  2. public class Program  
  3. {  
  4.    public static void Main()  
  5.    {  
  6.       Base objBase = new Base();  
  7.       objBase.Message(); // I amd Base  
  8.   
  9.       Derived objDerived = new Derived();  
  10.       objDerived.Message(); // I am Derived  
  11.   
  12.       // Now, set the reference of derived class to base class.  
  13.   
  14.       objBase = new Derived();  
  15.       objBase.Message(); // I am Derived  
  16.   
  17.    }  
  18. }  
  19.   
  20. public class Base  
  21. {  
  22.    public virtual void Message()  
  23.    {  
  24.       Console.WriteLine("I am Base");  
  25.    }  
  26. }  
  27.   
  28. public class Derived : Base  
  29. {  
  30.    public override void Message()  
  31.    {  
  32.       Console.WriteLine("I am Derived");  
  33.    }  
  34. }  
  Executing Code URL: DotNetFiddle.
  
  
• If method in the base and derived class are same and not made virtual in the base class and not being override in the derived. Also, new keyword is being applied with the derived class method then following case happens:
  
  1. using System;   
  2. public class Program  
  3. {  
  4.    public static void Main()  
  5.    {  
  6.       Base objBase = new Base();  
  7.       objBase.Message(); // I amd Base  
  8.   
  9.       Derived objDerived = new Derived();  
  10.       objDerived.Message(); // I am Derived  
  11.   
  12.       // Now, set the reference of derived class to base class.  
  13.   
  14.       objBase = new Derived();  
  15.       objBase.Message(); // I am Base  
  16.   
  17.    }  
  18. }  
  19.   
  20.   
  21. public class Base  
  22. {  
  23.    public void Message()  
  24.    {  
  25.       Console.WriteLine("I am Base");  
  26.    }  
  27. }  
  28.   
  29. public class Derived : Base  
  30. {  
  31.    public new void Message()  
  32.    {  
  33.       Console.WriteLine("I am Derived");  
  34.    }  
  35. }  
  Output:
  
  I am Base
  I am Derived
  I am Base
  
  Executing Code URL: DotNetFiddle.