Rudolf blog of all

This is something I was thinking about at the beginning of my TDI (Tabbed document interface) ‘adventure’ but I didn’t think it would be easy or possible back then. Then I came across a custom tab control (A highly configurable MDI tab control from scratch) that actually allowed you to use plain old WinForms to add to it. The control itself was written in VB and ultimately I abandoned using it but I was intrigued with how it could use a plain WinForm. It actually has some real advantages like.

• A form you can design easier in the IDE (than a user control).
• A form can be tested/used separately on it own without being embedded onto something else first.
• And I had a blank thinking of more reasons…

If you try to just add a Form to another container – like a panel, tabpage etc. and try to run it you would get the error: ‘Top-level control cannot be added to a control.‘. This happens because Forms are marked as Top Level controls. Fortunately, there is a simple way around it. You need to mark the form as not being a ‘Top level control’ like this: (assuming you have a panel called panel1)

Form f = new Form();
f.TopLevel = false;
panel1.Controls.Add(f);
f.Show(); //this is needed to actually have the form display itself inside the container

That will make the form load inside the panel without run-time errors – but it would look ugly if you just leave it like that. To properly ’embed’ it you need to add some more code:

Form f = new Form();
f.TopLevel = false;
f.MdiParent = null;
f.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
f.Dock = DockStyle.Fill;
panel1.Controls.Add(f);
f.Show();

So, there you have it!

Form2 f = new Form2();
            f.TopLevel = false;