Path.Combine for WebClient

Hi,

     I need help with the following:  I seem to not be able to use the IO.Path.Combine functionality when it comes to URI/URL type addresses.  It states that "URI formats are not supported.  I need this functionality as any part of my 3 to 4 part address and file name may either be empty or contain a trailing slash, or may not.  For file based scenarios, it works perfectly, but not for URI/URL type addresses.  Any help?

     Regards,

          Giovanni