if u want to add existing file means. right click the solution exp and add- existing file- choose only filename.csenough.it wil add to sol exp. then u can create object for that form in form1 - buton click event
Having different namespaces doesn't matter. Just while referencing to the form that you added, provide the full qualified path. Include the whole namespace path till your reach your desired Form Class. That should do the trick.