Server part of the application

There is a small C # application with the function of saving data in the xml file. There are no problems on the local machine with saving and reading, but the task was to write the server part, so that working with the file would be possible on the web. The question itself: I have never come across such a thing, so I ask you to show a simple skeleton of such a code or give links to resources where this question is well chewed, otherwise I did not find anything meaningful. Thanks a lot in advance.