Multi-file Upload (.NET)

Hi All,
I'm looking for .NET component that will allow me to implement multi-file upload. Now I found many on the Internet but none of them is satisfying my requirements. And I have two requirements really

1. It must not require installation of any components on client's machine (like java, flash, silverlight etc.)
2. It will allow for heavy customization which in fact translates to availability of source code to modify.

Now I can easily get around (2) by just developing UI in-house which would leave me only with the need of server side component (assembly) that would facilitate multi-file upload.

All suggestions very welcome!