How to upload a file on FTP Server in ASP.Net

Hi,
     I have a web application that provides the Users with option to upload their file to FTP Server. But when i try to do the same a security Exception is thrown.  I am unable to read remote file .
Please tell me a way to do the same , i cant use HTML or ASP.Net 2.0 File Upload Control . i have to use only FTP.
Thanks and Regards
Shrikant
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