This question asks how you embed a form in a TabPage from another form.
This questions and this question ask if it is possible to embed a form in a control in general.
This is something that I assumed you just couldn't do because why would you?
But, as the linked questions demonstrate, it is possible. And sometimes it appears to be necessary.
Hans Passant states that if you set the TopLevel property to false you get a
child window, almost indistinguishable from a UserControl
My question is:
What are the main reasons you would NOT do this?
Why specifically is it better to go through the effort of refactoring into a user control?
Before I saw these questions, I would have immediately assumed there must be (at the very least) a performance implication of embedding a form vs embedding a user control. I would have assumed there would be some additional overhead running for a form that does not run for a user control. But now I'm not so sure.
I would still do the refactor anyway (if I could) but I realised when viewing these questions that I don't have a concrete reason other than "it doesn't feel right to embed a form".