I have written code in my program that sets a key in the registry when my program is started so that if at a latter time a user double clicks a file with the extension that my program uses it will open my program. Now I need help with making my program open that file as well. I have no Idea how to have a file that is double clicked in Windows Explorer open in my program. Can someone show me some code to do this? What I am looking for is like when you double click a text.txt file it opens notepad and notepad opens the file.