Upload a file to Drupal server from (external) desktop client application (in c#) I have an application written in Winform (dotNet) and I would like it to Upload File to Drupal 7. 
I'm newbie in Drupal. Can somebody help me please?
You may want to create something with the Services module. The services module gives you an easy way to add REST / XMLRPC services to your drupal site. http://drupal.org/project/services

See also the documentation: http://drupal.org/node/736522