My application is only for me and co-workers, so I don\'t care if it\'s Click-Once or copy-the-exe. I want to be able to click a file with given extension in windows explor
Have you checked Environment.GetCommandLineArgs()? That shows the arguments with which your application was started.
Environment.GetCommandLineArgs()
If your application is associated with a file, it should contain the filename as one of the arguments.