You mentioned ASP.NET FileUpload control, so I will assume that are trying to enhance the FtpBrowserWeb sample to show a progress bar while a file is being uploaded. Please let me know if this is not the case.
When Rebex FTP is used in an ASP.NET web application, it runs at the webserver and only covers the process of transfering data between the webserver and an FTP server. The process of uploading a file from a user's web browser to the webserver is a separate task that is not handled by Rebex FTP.
In the FtpBrowserWeb sample, we used .NET's FileUpload WebControl to implement it. Unfortunately, this is only a simple control that doesn't support displaying any progress bar.
To add a progress bar, you would either have to use a third-party upload control for ASP.NET which supports displaying the progress bar or write our own (but this is actually quite complicated). Please check out this third-party blog post about progress bar in ASP.NET - its comments section also contains lot of additional information.