请高手解答：如何在vb.net中的webbrowser控件中绘图

[rockman_qp]

比如在webbrowser中绘制一个点或一条线之类的

Private Sub DrawMap(ByVal CurrentPos As Integer)

Dim penBrush As Brush = New SolidBrush(Color.Black)
Dim blackThinPen As New Pen(Color.Red)
Dim curPoint As Point

curPoint = GetMapCoordinate(CurrentPos)
blackThinPen.Width = 6

Dim graphic As Graphics = WebBrowser1.CreateGraphics()

graphic.DrawLine(blackThinPen, curPoint.X, curPoint.Y, LastPoint.X, LastPoint.Y)
graphic.DrawEllipse(blackThinPen, curPoint.X, curPoint.Y, 6, 6)
graphic.DrawEllipse(blackThinPen, 50, 100, 9, 9)

End Sub


3条语句都没有效果，望热心人指点，不胜感激