This property changes the display and behavior of the form to an MDI parent form. When this property is set to true, the form displays a sunken client area with a raised border. All MDI child forms assigned to the parent form are displayed within its client area.
When an MDI parent form is closed, the Closing events of all MDI child forms are raised before the MDI parent form's Closing event is raised. In addition, the Closed events of all MDI child forms are raised before the Closed event of the MDI parent form is raised.
If there are two MenuStrip controls on an MDI child form, setting IsMdiContainer to true for the parent form merges the contents of only one of the MenuStrip controls. Use Merge to merge the contents of additional child MenuStrip controls on the MDI parent form.