Picturebox覆盖vb.net

Question

I have written the following code but there is an issue which I am not trying to figure out.. I am trying to draw a simple line on the image in my picture box on mouse click. however, paint method is called but doesnt draw it, instead the line at that point is drawn when I scroll the picture in the picture box.. Pls help

Private Sub picCurrentimage_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles picCurrentimage.MouseDown
     px = e.X
     py = e.Y
     highlightPic(px, py)
End Sub

Private Sub highlightPic(ByVal x1 As Integer, ByVal y1 As Integer)
        haspoint = True
        picCurrentimage.Invalidate()
        picCurrentimage.Update()
End Sub


Private Sub picCurrentimage_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picCurrentimage.Paint
        If haspoint Then
            Dim g As Graphics = picCurrentimage.CreateGraphics
            Dim r As Rectangle = New Rectangle(px, py, 600, 10) 
            Dim pen As Pen = New Pen(Color.FromArgb(128, 32, 100, 200), 1) 
            Dim b As Brush = New SolidBrush(pen.Color)
            g.FillRectangle(b, r)
        End If
End Sub

Answer 1

Try to replace your code with the following modifications:

Private Sub highlightPic(ByVal x1 As Integer, ByVal y1 As Integer)
    haspoint = True
    picCurrentimage.Refresh()  'this do both of your lines in one
End Sub

Private Sub picCurrentimage_Paint(ByVal sender As Object, _
                                  ByVal e As PaintEventArgs) _
                                  Handles picCurrentimage.Paint
    If haspoint Then

        Dim g As Graphics = e.Graphics
        Dim r As Rectangle = picCurrentimage.ClientRectangle

        Dim b As Brush = New SolidBrush(Color.FromArgb(128, 32, 100, 200))
        g.FillRectangle(b, r)
        b.Dispose

    End If

End Sub