We don't have any built in file upload service that is designed to work with a desktop app. In the web application we have an authenticated user and we control upload permissions and locations based on roles. So we depend on the authentication cookie and role cookie features of being a web application. You would have to build your own service and figure out how to pass in credentials securely. Maybe you could use a web browser control (if it can accept cookies) inside your desktop app and create your own custom web page for it to use based on example code in mojoPortal.