Small problem with label or textbox updates

[skid2964]

I have a small, yet annoying problem. When I perform a "FOR" or "DO", I want to update a label or textbox as the loop progresses, for example: if I want to display a percentage done while incrementing a ProgressBar. The problem is that the label or textbox will never update, it wont even clear when I restart the loop!

simplified code example:

The label clear and = i never happen, only the "Done!"

ProgressBar1.Value = 0
ProgressBar1.Maximum = 150

Label1.Text = " "

        For i = 0 To 150

            ProgressBar1.Increment(2)
            i += 1
            System.Threading.Thread.Sleep(5)
            
            Label1.Text = i

        Next

Label1.Text = "Done!"

[Edneeis]

That is because you are sleeping the thread or otherwise processing which doesn't give the UI time to actually show the changes. Just add an Application.DoEvents right after you change the text in the loop and it should show then.

[Bazza81]

ProgressBar1.Value = 0
ProgressBar1.Maximum = 150
 
Label1.Text = " "
 
        For i = 0 To 150
 
            ProgressBar1.Increment(2)
            i += 1
            System.Threading.Thread.Sleep(5)
            
            Label1.Text = i
 
            [B]Application.DoEvents()[/B]             
 
        Next
 
Label1.Text = "Done!"

[skid2964]

Originally posted by Edneeis
That is because you are sleeping the thread or otherwise processing which doesn't give the UI time to actually show the changes. Just add an Application.DoEvents right after you change the text in the loop and it should show then.

Thanks!

[Andy]

does that take care of refreshing the control as well? I did one of these but all I used were longer loop times and a refresh statement. I heard that the application.doevents() isn't really desirable in any situation. dont know why.

[Edneeis]

What Application.DoEvents does is allow/force all of the threads in a process (possibly other processes as well) to work or update. This is bad in that if you are looping and there is no need for it then it makes the looping thread slower since it spends time waiting for other threads. This is good because sometimes you wait other threads to update, like the UIThread, even though it will eat clock cycles.