Visual Basic

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim frm2 As New Form2
        frm2.MdiParent = Me
        frm2.Show()
    End Sub
End Class

Public Class Form2

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim frm3 As New Form3
        frm3.MdiParent = Me.ParentForm
        frm3.Show()
    End Sub

End Class

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim frm3 As New Form3
        frm3.MdiParent = Me.MdiParent
        frm3.Show()
    End Sub

Public Function myCallBack(ByVal lwnd As Long, ByVal lpVHdr As Long) As Boolean
        Dim VideoData() As Byte
        Dim gh As Runtime.InteropServices.GCHandle _
            = Runtime.InteropServices.GCHandle.Alloc _
                (lpVHdr, Runtime.InteropServices.GCHandleType.Pinned)

        Dim AddrOflpVHdr As IntPtr = gh.AddrOfPinnedObject()

        Dim VideoHeader As New VIDEOHDR
        Marshal.PtrToStructure(AddrOflpVHdr, VideoHeader)

        gh.Free()

    End Function

<br />
    Structure VIDEOHDR<br />
        Dim lpData As Integer '// address of video buffer<br />
        Dim dwBufferLength As Integer '// size, in bytes, of the Data buffer<br />
        Dim dwBytesUsed As Integer '// see below<br />
        Dim dwTimeCaptured As Integer '// see below<br />
        Dim dwUser As Integer '// user-specific data<br />
        Dim dwFlags As Integer '// see below<br />
        <VBFixedArray(3)> Dim dwReserved() As Integer '// reserved; do not use}<br />
<br />
        'UPGRADE_TODO: "Initialize" must be called to initialize instances of this structure. Click for more: 'ms-help://MS.VSCC/commoner/redir/redirect.htm?keyword="vbup1026"'<br />
        Public Sub Initialize()<br />
            ReDim dwReserved(3)<br />
        End Sub<br />
<br />
    End Structure<br />