Multiple file format supporting Notepad application

Many years ago when Windows was young they invented Object Linking and Embedding (OLE). That technology has evolved but still exists with newer names and is easier to use. The KB article How To embed and automate Office documents with Visual Basic describes OLE but the details are not relevant to managed code.

I don't know the details of how to do it in managed code but there is probably a way to get information about what object to use for an extension. For example, you need to know that for a doc extension you need to use Word. However you do it, you need to be able to determine what control to use to show each type of file.

I think that the ContainerControl Class is the .Net way to embed an object and note that the Form class is derived from it, so that probably makes it quite easy to embed an OLE document into a form. I don't know trhe details of how to do it.