vb.net - 尝试删除以前在 Visual Basic 中创建的边框

Question

我有这个代码:

Sub drawborder()
    Dim objGraphics As Graphics
    objGraphics = Me.CreateGraphics
    objGraphics.Clear(System.Drawing.SystemColors.Control)
    objGraphics.DrawRectangle(System.Drawing.Pens.Red, picShowPicture.Left - 1,    picShowPicture.Top - 1, picShowPicture.Width + 1, picShowPicture.Height + 1)
    objGraphics.Dispose()
    borderstatus.Text = "Border Drawn"
End Sub

这会在图片框周围绘制一个边框。现在我想用另一个按钮再次删除它，但我似乎无法让它工作。

Answer 1

不要使用 CreateGraphics ，这只是一个临时绘图，当您最小化表单或将其移出屏幕等时，它将被删除。

尝试持有一个变量，然后使表单无效:

Private _ShowBorder As Boolean

Public Sub New()
  InitializeComponent()
  Me.DoubleBuffered = True
End Sub

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
  _ShowBorder = Not _ShowBorder
  Me.Invalidate()
End Sub

Protected Overrides Sub OnPaint(e As PaintEventArgs)
  e.Graphics.Clear(Me.BackColor)

  If _ShowBorder Then
    e.Graphics.DrawRectangle(Pens.Red, PictureBox1.Left - 1, PictureBox1.Top - 1, PictureBox1.Width + 1, PictureBox1.Height + 1)
  End If

  MyBase.OnPaint(e)
End Sub