Integrating an application in the windows shell?

I am creating a file-sharing application I want to integrate into a windows shell. I am writing the core in portable C but the windows GUI in C#.

What I want to achieve is to for example add custom selection/option when you right-click a file (like, WinRAR adds custom option when you right-click a file, it allows you to rar the f开发者_开发百科ile and whatnot). I am not sure what the term is called though.

How do you do this in C#?

Thanks!

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You're talking about something called a "shell extension". There are degrees of complexity associated with doing this sort of thing, as with everything. This is a good starting point and example; searching Google for "C# shell extension" returns lots of useful links.