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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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 Usage Notes
   ■ Only one form in an application can be a container form. If you try
     to set a second form's FormType property to MDI (1), Visual Basic
     generates the error message, "MDI container already exists." The
     previous container form must be set to a standard form (Normal = 0)
     before a new one can be set.
 
   ■ An MDI or container form functions like a standard form, with the
     following exceptions:
     • The container form is always maximized. Move, Size, Minimize, and
       Restore are disabled when the form is visible.
     • The container form can display a visible border style (BorderStyle
       <> 0). This allows display of a title bar and use of the Control-menu
       box to close the application. Note: If no border is specified
       (BorderStyle = 0), the client area will be the same as the screen size
       (minus the menu).
     • The MinButton, MaxButton, WindowState, Height, Width, Top, and Left
       properties are read-only at design time and run time.
     • The MOVE method is not supported at run time.
     • The container form can only contain menu controls. Child forms can
       contain menus, but they will be displayed on the container form.
 
   ■ All other forms in the project become children of the container form.
     The following rules apply:
     • Loading a container does not automatically load its children; however,
       loading a child form automatically loads the container. Unloading the
       container unloads all children.
     • Making the container invisible makes all children invisible. The
       visibility (Visible property) of a child form is independent of the
       container; however, the container must be visible before "visible"
       children can be seen. Note: Making the container visible only makes
       the container and any children previously visible appear.
     • Disabling or enabling a child form is independent of the container
       form; however, the container must be enabled before children are truly
       enabled. Making the container form enabled only enables the container
       and any of its children that were previously enabled.