Drawing an rectangle around the panel

[aashish_9601]

I have used this code to draw an rectangle around the panel

Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
With Panel1
            e.Graphics.DrawRectangle(Pens.Gray, .Left - 1, .Top - 1, .Width + 1, .Height + 1)
        End With
End Sub

but when the form is resized the rectangle isnt drawn properly. The panel has Left,R,T,B anchor.

[stateofidleness]

try removing the anchor.. seems like that would conflict with the code positioning.

[jmcilhinney]

Can you not just set the BorderStyle of the Panel?

[aashish_9601]

try removing the anchor.. seems like that would conflict with the code positioning.

I cant remove the anchor as i want to panel to resize along with the form.

Can you not just set the BorderStyle of the Panel?

No i cant. Actually i want the border to be in Gray color and 1 pixel away from the panel

[stateofidleness]

Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
   With Panel1
       e.Graphics.DrawRectangle(Pens.Gray, .Left - 1, .Top - 1, .Width + 1, .Height + 1)
   End With
End Sub
 
Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
    Me.Refresh()
End Sub

[jmcilhinney]

The problem is that resizing doesn't cause the entire form to be invalidated, so the entire form isn't redrawn. Call the form's Invalidate method in its Resize event handler to change that behaviour. You may have some issue with flickering, depending on how complex your form is. In that case set DoubleBuffered to True. If there are still issues then you'll have to look at other options.

[stateofidleness]

thought about that jmc, but i just tested the Refresh call on a whim and it worked great with no flickering issues even! Should do what he wants.

[jmcilhinney]

thought about that jmc, but i just tested the Refresh call on a whim and it worked great with no flickering issues even! Should do what he wants.

Refresh internally calls Invalidate followed by Update. Invalidate specifies what area needs to be redrawn on the next repaint. It can be called multiple times to specify multiple areas. Update actually does the repaint. I'm not sure but calling Refresh may end up causing twice as many repaints as needed.

[aashish_9601]

Private Sub From1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
        Dim rec As New Rectangle(Panel2.Left - 1, Panel2.Top - 1, Panel2.Width + 1, Panel2.Height + 1)
        Dim r As New Region(rec)
        Me.DoubleBuffered = True
        Me.Invalidate(rec)
    End Sub

I have used this code as suggested. Not much sure if its correct as i have used the invalidate method first time.

The design of my form is very simple, not many controls in it. The flickering occurs even though the DoubleBuffered is set true.

[jmcilhinney]

Think about it. Would you set DoubleBuffered to True every time there's a Resize event? Do you ever set it to False? If not, why do you need to keep setting it to True over and over? It's no different to any other form property. Set it in the designer and be done with it.

I tested with just a Panel and nothing else on the form and DoubleBuffered left False, plus I called Invalidate without arguments. I saw no flickering. What happens when you try that?

[aashish_9601]

ok Done with DoubleBuffer.

Actually inside my panel
1. I am drawing a line
2. Contains another panel in which i am drawing 2 rectangles an 1 line.

These both are flickering