When I was giving the interview I was getting this question in all interview. So I am sharing this short answer for everyone.
This all keywords looks like used for same purpose and there are some differences in each one.
One time i got this question in interview. Answer of this question , i have implemented in this code like this
public partial class _Default : System.Web.UI.Page
protected void Page_Load(object sender, EventArgs e)
//The is operator is used to check whether the run-time type of an object is compatible with a given
if (num is int)
Response.Write(“Num is integer”);
//The as operator is used to perform conversions between compatible types.
object ss = “This sis the string”;
string str = string.Empty;
if (ss is string)
str = ss as string;