How to customize the height of border displayed at the bottom of MDIChildForm header in WinForms TabbedMDIManager?
Customize the border height
In TabbedMDIManager, it is possible to customize the height of border displayed at the bottom of MDIChildForm header, by using the property named “BottomBorderHeight”.
C#
TabHost tabHost = this.tabbedMDIManager1.GetTabHostFromForm(frm); //To customize the border height of the TabControl tabHost.BottomBorderHeight = 0;
VB
Dim tabHost As TabHost = Me.tabbedMDIManager1.GetTabHostFromForm(frm) 'To customize the border height of the TabControl tabHost.BottomBorderHeight = 0
Screenshot

Fig 1. Before reducing inner border height of Tab Control with image

Fig 2. After reducing inner border height of Tab Control with image
Samples: