You'll have to experiment with this, but you should be able to do this via code. I.e. something like this:
//-- Instantiate form, set it to be NOT top level.
MyChildForm frm = new MyChildForm();
frm.TopLevel = false;
//-- Add this to the form's collection of controls.
this.Controls.Add(frm);
//-- You still have to call show...
frm.Show();
A couple of things to note:
- You have to set the TopLevel property to false, otherwise you'll get a "Top-level control can't be added to a control" exception.
- You must also show the added form, or you won't see anything.
- You can add it to other containers. E.g. a panel, a splitter control's panel, etc.
- The form will be movable and sizable if configured.