Upcasting and downcasting in C#

Downcasting:

By taking child class object referance  CLR will find the parent class referance

Sample code:

{

B b=new B();

Response.write(b.x);

Response.write(b.y);

A a=b;           // downcasting

Response.write(a.x);

Response.write(a.y);

 }

}

public class A

 {

   public int x=10;

  public string y="hello";

}

public class B:A

{

  public int x=20;

   public string y="palle";

}

Upcasting:

In case of upcasting technique CLR identify the child class object  referance by using parent  class object

sample Code:

public partial class inh : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        Student2 s2 = new Student2();

        Student1 s1 = s2;              //Downcasting which is implicit operation

        Response.Write(s1.name);                      

        Response.Write(s1.stud_id);

       Student2 s3 = (Student2)s1;   //Upcasting which is explicit operation

        Response.Write(s3.name);               //Output--->Kripa

        Response.Write(s3.stud_id);           //Output--->1002

         }

}

public class Student1

{

     public string name = "kumar";

     public int stud_id = 1001;
 }
 public class Student2 : Student1
 {
      public string name = "Kripa";
      public int stud_id = 1002;
 }
 }
Note:

->In the above sample code first downcasting operation performswhere finding the parent 

class object reference through the child class object reference(Student s1=s2)

,where s1 is parent class object and s2 is child class object.

->By using parent class object reference we have to find child class 

object reference which is upcasting 

->(Student2 s3=(Student2)s1),where s3 is child class object and s1 is parent parent

 class object.