How do you acheive this in ASP.NET?

[jeba]

Hi there!

What is the equivlent of the following ASP code in ASP.NET?
please help.

Sub ValidateValue()
      if Condition=False then
     %> 
         <SCRIPT LANGUAGE=javascript> 
        <!-- 
              alert("I want to display a msg here & then redirect!"); 
             //otherwise I would have used Response.Redirect("mainpage.aspx")
            document.location.href="mainpage.asp"; 
        //--> 
       </SCRIPT> 
     <% 
          Response.End 
     end if
End sub