ASP.NET Question

how to implemet this in
If isnothing(session("ssnLogin")) = True Then
Response.Redirect("loginpage.aspx")
End If

bcoz there is no such IsNothing method in C#.Net

Write your code like

If(Session["ssnLogin"] == null)
 {
     Response.Redirect("loginpage.aspx");
 }

Thanx Sir,It helped but i have one more problem that if there is master page already operated with default.aspx page and i have one more page that is about.html and if i want that in contentplaceholder of master page i want to show the data that is written in about.html in runtime is this possible or not?

Check the session. If login is successful u need to set one session. so check this session in every page load.

If isnothing(session("ssnLogin")) = True Then 
     Response.Redirect("loginpage.aspx")
End If

put answer 4 code in master page .cs file (page_load event). use iframe to display html in same page at runtime.