multipart/form-data fails to recognize post-data when handling download requests by the client

[GoogleCodeExporter]

What steps will reproduce the problem?
1. handle the event DownloadRequestAsync (used HttpWebRequest in this case)
2. have the control navigate to 
http://www.cs.tut.fi/~jkorpela/forms/testing.html
(contains some various form tests)
3. attempt to submit to the multipart/formdata form and trace the results

when handled by IE (or the control without client handled downloads), the 
example gives a proper multipart/formdata dump. When RequestDownloadAsync 
is handled, the post data byte array is never set. application/x-www-form-
urlencoded is handled fine. Using a string replacement alogorithm, changing 
the form encoding type to application/x-www-form-urlencoded revealed post 
data.

What are the OS and IE versions?
IE: 7.0.5730.13
OS: WinXP (both SE2 & SE3)

What exceptions are thrown? If any, please copy and paste the exception 
dump.

No exceptions are thrown, but AsynchDownloadRequestEventArgs.Post is set to 
null.

What is the expected output? What do you see instead?
The expected output is a raw post data in the format of multipart/form

Original issue reported on code.google.com by rpce...@gmail.com on 23 Mar 2010 at 8:29