ASP.NET - files copy into physical location without over write the files

i have table for file names




id  filename                   orginalname
1   32-degits(guidno)             asp.docx


2   32-degits(guidno)               c#.docx


3   32-degits(guidno)             asp.docx




i save my files rename(16-degits(guidno)) and save. at time of downloaded rename and send to enduser.


now


1) i want to download every file into one folder with orginalnames. at time dont want  overwrite and fileexit messages.[How can i achieve this.]


2)  this will make it as one-zip file and provide download option. 




please suggest me. thanks in advance.