You need to change the following line:
= System.IO.Path.Combine(filepath, filename & f.GetExtension)
= System.IO.Path.Combine(Server.MapPath(filepath), filename & f.GetExtension)
Expect from that, everything else works correctly. I have prepared sample project that demonstrates the approach, you can find it as an attachment.
This forums is for ASP.NET controls, not for WindowsForms ones. I suggest that you navigate to this link
and open a thread describing your problem there.
the Telerik team