Is it bad to use a Windows Form as a Control?

Question

I know it's possible to use a Form as a child control in another Form.

ChildForm child = new ChildForm();
child.TopLevel = false;
child.FormBorderStyle = FormBorderStyle.None;
child.Show();
containerControl.Controls.Add(child);

I realise this is not what a Form was designed for. I was wondering what the implications here are, as opposed to using a UserControl ? Are there any real downsides? Any large, unnecessary overheads? Any unexpected behaviours?

On the other hand, are there any advantages of using a form? Is there anything you can't do with a UserControl that you can do with a form, which may be useful if used as a child control?

I understand that both Form and UserControl inherit ContainerControl , but how different do their non-inherited members make them?

My scenario

The reason I'm asking is because I have an existing Form control, that I'd like to be displayed on its own sometimes (for development and as a little extra feature), but it doesn't need to be. However, I do need the Closing event of the form (which is not inherited from ContainerControl ) and I need to be able to cancel closing the form if a file has been edited and not saved.

I've also noticed in my findings that a Form seems to have some transparency options that a UserControl doesn't seem to have, but I'm not sure if these will work when the form is used as a child control.

Answer 1

if you check the Inheritance Hierarchy in MSDN you find out that both UserControl and Form inherit from ContainerControl so in fact up to their base class nearly everything should be the same.

said so, in general, I think you should avoid using a Form object hosted as a control unless you are dealing with legacy unchangeable code or unless you absolutely want this design so to be able, in certain other cases, to show the form all alone as top level non hosted anywhere.

If you simply need a container to put your other UI controls you can use a UserControl.

in fact everything down to the Win32 level translates to handles and message pumps / WindowProc etc, even a simple TextBox will have an handle and will receive and consume messages taking care of its client and non client area and so on.