Just load a new dummy MenuStrip to the ParentForm.
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.IsMdiContainer = True
Me.MainMenuStrip = New MenuStrip
Dim ChildForm As New Form2
ChildForm.WindowState = FormWindowState.Maximized
ChildForm.MdiParent = Me
ChildForm.Show()
End Sub
VB.NET to C#
http://www.developerfusion.com/tools/convert/vb-to-csharp/