问如何按预期顺序绘制子控件和自定义绘图？

EN

GraphicsPath path = new GraphicsPath();
// add some shapes to path here, describing the control shape
// ...
this.Region = new Region(path);

Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)       'This is traps the default OnPaint for a Component, so it starts by calling the Base's Paint Event
    MyBase.OnPaint(e)

    'Add your custom paint code here - in this example, a Green Arrow
    AddArrowOverHeaderCheckBox()        
End Sub
Private Sub AddArrowOverHeaderCheckBox()
    'Adds an Arrow that is placed over the Checkbox of the 0th row, of a ListView, (over a Row that is used as a Header in this Custom Control).

    'Create a Rectangle into which to put the arrow
    Dim G As Graphics = Me.CreateGraphics               'Attach a Graphics Object to the Base
    Dim lvsi As ListViewItem.ListViewSubItem = Me.Items(0).SubItems(0)   'Get the first row; it is being used as a header in this case
    Dim CheckBoxWidth As Integer = Me.Bounds.X          'Calculate the size of the Control's CheckBox
    Dim CheckBoxHeight As Integer = lvsi.Bounds.Height
    Dim InflateBy As Integer = 1                        'Optional amount to resize the area in which the Arrow is to be placed
    Me.Refresh()                                        'Refresh the ListViewTab so that it does not overpaint the arrow that is about to be created at the End Sub
    Dim I As Integer = 0
    I = (CheckBoxHeight + 1) Mod 2
    Dim R As Rectangle = New Rectangle(lvsi.Bounds.X + Me.Margin.Left, lvsi.Bounds.Top, CheckBoxWidth, CheckBoxHeight + I) 'Make sure the height is an Odd number, to make a tidy arrow
    'myBrush.Color = Color.Red
    R.Inflate(InflateBy * 2, InflateBy)                  'Create a covering rectangle that is larger than the CheckBox on the Left of the CheckView Item in both dimensions
    Dim myBrush As New System.Drawing.SolidBrush(Me.BackColor)
    G.FillRectangle(myBrush, R)                         'Draw a filled Rectangle over the CheckBox in the Background colour for the ListViewTab to obscure the CheckBox
    Dim RW = R.Width
    Dim RH = R.Height
    I = CSng(RH) * 0.5 \ 2                              'Set a proportion of the arrow's width for its shaft, here 50%
    If RH Mod 2 <> 0 Then RH += 1                       'Ensure that the Height is an Odd number to make the Arrow axially symmetric
    '                                                   'Create a polygon in an Arrow shape that fits inside the Rectangle
    Dim polyArrow As Point() = {New Point(R.X + 0, I + R.Y), New Point(R.X + RW * 0.4, I + R.Y), New Point(R.X + RW * 0.4, 0 + R.Y), New Point(R.X + RW, RH * 0.5 + R.Y),
                                New Point(R.X + RW * 0.4, RH + R.Y), New Point(R.X + RW * 0.4, RH - I + R.Y), New Point(R.X + 0, RH - I + R.Y)}
    Dim path As New Drawing2D.GraphicsPath()            'Create a Path shaped like an Arrow & sized proportionately to the size of the required Rectangle
    path.AddPolygon(polyArrow)                          'Turn the Path into a polygon
    Dim [reg] As New [Region](path)                     'Define a Graphics Region of the shape of the Arrow
    G.SetClip([reg], combineMode:=Drawing2D.CombineMode.Replace) 'Redefine the area; clipping will now prevent any drawing outside the area of the Arrow
    myBrush.Color = Color.Green
    G.FillRectangle(myBrush, R)                         'Draw a filled Green Rectangle, clipped to the Path shape
    'Dim pen As Pen = Pens.Black                         'Optionally: Draw a fine boundary in black
    'G.DrawPath(pen, path)                               'Optionally: Draw a fine boundary in black
    G.SetClip(Me.ClientRectangle)                       'Remove the Clip from the Graphics area - in case G is re-used
    myBrush.Dispose()                                   'Tidy up
    G.Dispose()
End Sub