Permissions needed to copy a file to a UNC share

I'm working on and ASP.NET app. A key functionality is that it copies a pdf document to a share on FILE_SERVER_1. I'm using the System.IO.File.Copy method to copy the file.

When I run locally (from the debugger), everything works fine. When I run the app from WEB_SERVER_1, I get an UnauthorizedAccessException. I presume that this is becau开发者_C百科se on the server, the app is running as the NETWORK SERVICE. I've given NETWORK SERVICE Modify and Write privileges on the folder and on the share on FILE_SERVER_1, but I still get the exception.

What else do I need to do?

https://serverfault.com/questions/41130/network-service-account-accessing-a-folder-share