Visual Basic

    Private Sub MDIParent1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
<br />
        Dim ChildForm1 As New System.Windows.Forms.Form<br />
        Dim btnButton1 As New Button<br />
        Dim ChildForm2 As New System.Windows.Forms.Form<br />
        Dim btnButton2 As New Button<br />
        ChildForm1.Text = "Form1"<br />
        ChildForm2.Text = "Form2"<br />
        btnButton1.Text = "I Control 2"<br />
        btnButton2.Text = "I Control 1"<br />
        ChildForm1.MdiParent = Me<br />
        ChildForm1.Controls.Add(btnButton1)<br />
        ChildForm1.Show()<br />
        ChildForm1.Name = "Form1"<br />
        ChildForm2.MdiParent = Me<br />
        ChildForm2.Controls.Add(btnButton2)<br />
        ChildForm2.Show()<br />
        ChildForm2.Name = "Form2"<br />
<br />
<br />
        AddHandler btnButton1.Click, AddressOf button_click<br />
        AddHandler btnButton2.Click, AddressOf button_click<br />
    End Sub<br />
<br />
    Sub button_click(ByVal sender As Object, ByVal e As EventArgs)<br />
        For Each frm As Form In Me.MdiChildren<br />
            If frm.Name <> sender.parent.Name Then<br />
                If frm.Visible Then<br />
                    frm.Hide()<br />
                Else<br />
                    frm.Show()<br />
                End If<br />
            End If<br />
        Next<br />
    End Sub