UI freeze when long process done in BackgroundWorker class.

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I am created an application where create more than 700 Labels in flowLayoutPanel. the creation process done in DoWork event of BackgroundWorker Class, but when the process started then the UI freeze.
I read and search all the tutorial about BackgroundWorker class and I follow the instruction, ultimately UI freeze when the Backgroundworker is in the processing.
My code is:

private void button1_Click(object sender, EventArgs e)
       {
           backgroundWorker1.RunWorkerAsync();
       }

       private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
       {
           List<Label> lblList = new List<Label>();
           for (int i = 1; i <= totaElement; i++)
           {
               Label lbl = new Label();
               lbl.Name = "lbl" + i;
               lbl.Text = i.ToString();
               lbl.BorderStyle = BorderStyle.FixedSingle;
               lbl.AutoSize = true;
               lblList.Add(lbl);
               backgroundWorker1.ReportProgress(i);
           }
           e.Result = lblList;
       }

       private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
       {
           int percentage = ((e.ProgressPercentage * 100) / 1000);
           progressBar1.Value = percentage;
       }

       private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
       {
           List<Label> CreatedLbl = (List<Label>)e.Result;
           flowLayoutPanel1.SuspendLayout();
           flowLayoutPanel1.Controls.AddRange(CreatedLbl.ToArray());
           flowLayoutPanel1.ResumeLayout();
       }

I download this[^] article's Demo and it's worked perfectly, but I couldn't find out my mistakes..

How to fix this problem?
How to free the UI ?
thanks in advanced..

Regards
Jayanta.

Posted 25-Jun-15 5:15am

JayantaChatterjee

Updated 25-Jun-15 5:21am

v3

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Comments

[no name] 25-Jun-15 11:27am

"create more than 700 Labels", you really do not see the problem here?

JayantaChatterjee 25-Jun-15 11:33am

I know that is big process, but that is in BackgroundWork class DoWork,
it suppose to not freeze the UI?

[no name] 25-Jun-15 11:43am

It normally would not but you are doing UI work in your background thread! And, creating 700 labels tells everyone out here that you need to redesign your application. There is probably no reason at all for 700 labels to be created and shown to a user.

JayantaChatterjee 25-Jun-15 12:03pm

I don't want to show the creation process to the user, Only I want to give the option to cancel the process. In this scenario the UI is freezed so user can not have that(Cancel) option..

My question is :
how to provide the cancel option to the user??

SteveHolle 25-Jun-15 12:26pm

Where is the UI work in the background thread? I see loading a list and returning it on completion?

F-ES Sitecore 25-Jun-15 11:49am

Are you sure it isn't hanging the UI when doing the completed event? As the code inside that looks like it would freeze the UI. Try commenting out the code in the completed event, maybe replace it with a Sleep(3000) or something, and see if you still get UI freeze. If you don't then the issue is probably just the updating on the UI, which has to occur on the main GUI thread.

JayantaChatterjee 25-Jun-15 12:12pm

Yes you are right hanging the UI on Complete Event of BackgroundWorker.
I change my code:
private void button1_Click(object sender, EventArgs e)
{
flowLayoutPanel1.SuspendLayout();
backgroundWorker1.RunWorkerAsync();
}

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
List<Label> lblList = new List<Label>();
for (int i = 1; i <= 1000; i++)
{
Label lbl = new Label();
lbl.Name = "lbl" + i;
lbl.Text = i.ToString();
lbl.BorderStyle = BorderStyle.FixedSingle;
lbl.AutoSize = true;
lbl.BackColor = Color.LightSalmon;
lbl.ForeColor = Color.DarkViolet;
lblList.Add(lbl);
backgroundWorker1.ReportProgress(i,lbl);
}
e.Result = lblList;
}

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
int percentage = ((e.ProgressPercentage * 100) / 1000);
progressBar1.Value = percentage;
Label lbl =(Label) e.UserState;
flowLayoutPanel1.Controls.Add(lbl);
}

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
//List<Label> CreatedLbl = (List<Label>)e.Result;
//flowLayoutPanel1.SuspendLayout();
//flowLayoutPanel1.Controls.AddRange(CreatedLbl.ToArray());
flowLayoutPanel1.ResumeLayout();

}

but it also hanging my UI...
so I want to give the option to cancel the process to the user..
how it is possible(in this scenario )?

F-ES Sitecore 25-Jun-15 12:18pm

Bulk updates are always going to freeze the UI. You could show a modal "please wait" box while it happens, or you could update the labels in smaller batches, calling DoEvents between updates to allow the UI to still be responsive.

JayantaChatterjee 25-Jun-15 12:20pm

Thank You all..
I solve my problem by sending the thread to sleep for 50 millisecond in DoWork event, and it worked like animation... :-)
Thanks a Lottt @F-ES....

Sreekanth Mothukuru 26-Jun-15 8:32am

JCahyaatnttearjee: Post your fix under Solution so that it no longer appear in unanswered list.

JayantaChatterjee 26-Jun-15 8:33am

Okay..

2 solutions

Solution 2

What nobody has said is that creating UI controls in a background thread is a horrible idea. Don't get into the habit of it. It may appear to work on the surface and in testing but your controls may not work properly.

UI controls should ALWAYS be created on the UI thread.

On top of that, creating 1000 labels is just going to kill your forms redraw performance.

Posted 26-Jun-15 3:23am

Dave Kreskowiak

Comments

JayantaChatterjee 27-Jun-15 5:25am

thanks for suggestion..
I know this process(which I did) is not good for performance..
here I am making this application to doing some test with worker thread, so that's why I'm making this type of concept with Winforms controls..
most importantly I'm not include it with my habit.. :-)

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JayantaChatterjee · Accepted Answer · 2015-06-26T02:41:00

Here is my final code:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {            
            for (int i = 1; i <= 1000; i++)
            {
                Label lbl = new Label();
                lbl.Name = "lbl" + i;
                lbl.Text = i.ToString();
                lbl.BorderStyle = BorderStyle.FixedSingle;
                lbl.AutoSize = true;
                lbl.BackColor = Color.LightSalmon;
                lbl.ForeColor = Color.DarkViolet;            
                Thread.Sleep(50);
                backgroundWorker1.ReportProgress(i,lbl);
            }            
        }

        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            int percentage = ((e.ProgressPercentage * 100) / 1000);
            progressBar1.Value = percentage;
            Label lbl =(Label) e.UserState;
            flowLayoutPanel1.SuspendLayout();
            flowLayoutPanel1.Controls.Add(lbl);
            flowLayoutPanel1.ResumeLayout();
        }

I changed the flowLayoutPanel1 update method, it updated on every Label creation on worker thread and also sending worker thread to sleep for 50 milliseconds(in the meantime the UI can update properly)..
and thanks to @F-ES Sitecore for the Idea...