I'm using SplitContainer (It's contain two panels) control under my MdifForm.I'm using following code to showing my exist forms under SplitContainer panel2

Code:
With My_Form
        .MdiParent = Me
        SplitContainer.Panel2.Controls.Add(My_Form)
        .My_Form_Activated(Me, e)
        .WindowState = FormWindowState.Maximized
        .Dock = DockStyle.Fill
        .Show()
    End With
Docking fill command work properly at first displaying of the My_Form. But after mdiform resizing, my_form size doesn't change. How can i fix this problem thanks.