' Create a new form.
Dim mdiChildForm As New Form

Private Sub Form1_Load(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load

    ' Set the IsMdiContainer property to true.
    IsMdiContainer = True

    ' Set the child form's MdiParent property to 
    ' the current form.
    mdiChildForm.MdiParent = Me

    'Call the method that changes the background color.
    SetBackGroundColorOfMDIForm()
End Sub

Private Sub SetBackGroundColorOfMDIForm()
    Dim ctl As Control

    ' Loop through controls,  
    ' looking for controls of MdiClient type. 
    For Each ctl In Me.Controls
        If TypeOf (ctl) Is MdiClient Then

            ' If the control is the correct type,
            ' change the color.
            ctl.BackColor = System.Drawing.Color.PaleGreen
        End If
    Next

End Sub

' 导入命名空间
Imports System
Imports System.Collections
Imports System.Data
Imports System.IO
Imports System.Xml.Serialization
Imports System.Windows.Forms
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Drawing.Text
Imports System.Drawing.Printing


Public Class MainClass
    Shared Sub Main()
       Dim form1 As Form = New Form1()
       Application.Run(form1) 
     End Sub
End Class







Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.Container

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(6, 15)
        Me.ClientSize = New System.Drawing.Size(292, 268)
        Me.Name = "Form1"
        Me.Text = "MDI Example 1"

    End Sub

#End Region

    Private Sub Form1_Load(ByVal sender As System.Object, _
   ByVal e As System.EventArgs) _
   Handles MyBase.Load
        Me.Text = "I'm an MDI Parent"
        Me.IsMdiContainer = True
        Dim MyChild As New System.Windows.Forms.Form()
        MyChild.MdiParent = Me
        MyChild.Show()
        MyChild.Text = "MDI Child"
    End Sub

End Class