File Upload To FTP using File Upload Control

Question

i want to upload file to FTP server using FileUpload control

 

its working file but when i check that is file is already present at that location if yes then it will ask that whether you want to overwrite that file or not.

 

for that i call javascript function from code behind where it show me message that i have to overwrite file or not?

but at that time file selected in FileUpload control disappear