急！GDI+在VB2005中的重绘问题，高手请进。

[AreZong]

我在窗体中放一PictureBox控件，然后在它上面绘图：

Private Sub Form1_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Activated
Me.PictureBox1.Refresh()
End Sub

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
MyBase.OnPaint(e)
End Sub

Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1_Draw.Paint
Dim g As Graphics = e.Graphics
sender.CreateGraphics().Clear(Color.Black)
g.DrawLine(System.Drawing.Pens.Red, 0, sender.Height / 2, sender.Width, sender.Height / 2)
End Sub

问题：
上面代码绘图没有问题，但当我用鼠标打开窗体的菜单覆盖了PictureBox1时，或当我切换到其它程式（如小画家），该程式覆盖了PictureBox1时，PicurtBox1中的所有已画的图都会给覆盖部份擦掉，不会自动恢复。

请问：
我该如何保持绘画？无论绘画区有没有被覆盖，只要已绘好的画就会象一幅图片一样保留着。

谢谢！！

[lgx1972]

首先你的代码在VB2005下测试失败。
问题出在这句上面了：g.DrawLine(System.Drawing.Pens.Red, 0, sender.Height / 2, sender.Width, sender.Height / 2)

然后回答你的提问：
把：Me.PictureBox1.Refresh() 这语句放在 Form1_Paint里，而不是放在Form1_Activated里
问题就解决了!

[AreZong]

楼上的，谢谢。
我把测试代码重新写过，如下，但还是不行啊。

你试着打开小画家（不要最大化，用小窗体），然后拖动小画家从PictureBox1上面慢慢地移过，你就知道了。
小画家会象粉笔擦一样擦掉PictureBox1上面的画。


Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.PictureBox1.Dock = DockStyle.Fill
Me.PictureBox1.BackColor = Color.Black
End Sub

Private Sub Form1_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Activated
Me.PictureBox1.Refresh()
End Sub

Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
Me.PictureBox1.Refresh()
End Sub

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
MyBase.OnPaint(e)
End Sub

Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
Dim g As Graphics = e.Graphics
sender.CreateGraphics().Clear(Color.Black)
g.DrawLine(System.Drawing.Pens.Red, 0, 100, sender.Width, 100)
End Sub

End Class

[AreZong]

楼上的 wzuomin ，
有什么高见啊？

[wzuomin]

Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.PictureBox1.Dock = DockStyle.Fill
        Me.PictureBox1.BackColor = Color.Black
    End Sub

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        e.Graphics.Clear(Color.Black)
        e.Graphics.DrawLine(Pens.Red, 0, 100, PictureBox1.Width, 100)
    End Sub

End Class

[AreZong]

3天了，没有答案，期待VB的绘画高手指教。。。

[AreZong]

To wzuomin :
不好意思，理解错了你的代码，原来就这么简单！
谢啦！

[niulei]

2楼正解！