Page contains the processing

We often want to use pages that contain things like this.
In asp.net  , I still used to use include   in asp, which was very troublesome to use.
Let me write asp.net   in
1. < script >
< script   src="top.aspx"   runat="server"/ >

2.include
< !--   INCLUDE   file="top.aspx"   -- >
< !--   INCLUDE   virtual="/my/top.aspx" >

3.   USES the user control
User controls provide flexible functionality.