Progress bar marquee with running process

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3.00/5 (1 vote)

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Hi, Please help me with my problem.

For example, I want to create a Label Text that counts into 100 - (this can be more than 100)
At the same process, as it is counting I want to show a Progress Bar while Label Text is Updating.

Since I don't want to report the progress, that's why I'm using Marquee and for loop below is just and example of the process.

I encountered below error in

C#

this.label1.Text += string.Format("{0}. This is a test.", i);

An exception 'Microsoft.VisualStudio.Debugger.Runtime.CrossThreadMessagingException' occurred

What I have tried:

C#

private void button1_Click(object sender, EventArgs e)
       {
           button1.Enabled = false;
           progressBar1.Style = ProgressBarStyle.Marquee;
           progressBar1.MarqueeAnimationSpeed = 50;

           BackgroundWorker bw = new BackgroundWorker();
           bw.DoWork += bw_DoWork;
           bw.RunWorkerCompleted += bw_RunWorkerCompleted;
           bw.RunWorkerAsync();
       }

       void bw_DoWork(object sender, DoWorkEventArgs e)
       {
           // INSERT TIME CONSUMING OPERATIONS HERE
           // THAT DON'T REPORT PROGRESS
           for (int i = 1; i <= 100; i++)
           {
               this.label1.Text += string.Format("{0}. This is a test.", i);

           }
           Thread.Sleep(100);
       }

       void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
       {
           progressBar1.MarqueeAnimationSpeed = 0;
           progressBar1.Style = ProgressBarStyle.Blocks;
           progressBar1.Value = progressBar1.Minimum;

           button1.Enabled = true;
           MessageBox.Show("Done!");
       }

Posted 31-Jul-16 17:11pm

berrymaria

Updated 1-Aug-16 4:54am

v5

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Philippe Mori 1-Aug-16 11:04am

You should never use Marquee style if you can compute the percentage... as it give less information to the user about progress.

2 solutions

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Philippe Mori · Answer 1 · 2016-08-01T04:54:00

You should read the documentation on BackgroundWorker before using one to properly understand how it works and should be used.

BackgroundWorker Class (System.ComponentModel)[^]

How to: Make Thread-Safe Calls to Windows Forms Controls[^]

Here are some similar questions :
c# - CrossThreadMessagingException while using backgroundworker windows forms - Stack Overflow[^]
multithreading - C# threading issue - Stack Overflow[^]

In your case, you usually want to enable progress reporting and then implement an handler to report progress.
BackgroundWorker.ReportProgress Method (Int32) (System.ComponentModel)[^]

Usually, I would compute the percentage inside DSoWork handler and only report progress if the percentage (as an integer) has changed. That way, you ensure that you don't update the UI more than 100 times which is adequate when a progress bar is displayed.

By the way, there is a version that allows to pass an UserState which could be used if you want to report something else than percentage. This is somewhat simpler and clearer than using Invoke directly.

It generally works quite well if you report progress up to a few hundreds of time. If you have many thousand updates, then you somehow need to optimize communications between threads to reduce the overhead of cross-thread calls.

Garth J Lancaster · Answer 2 · 2016-07-31T18:39:00

Solution 1

I'm not sure why you're setting progressBar1.Value = progressBar1.Maximum there - it may be something I dont know about the Marquee style .. that being said, I would have expected something like

C#

progressBar1.BeginInvoke( new Action( () => { progressBar1.Value = i; } ));

inside your 'for loop' - I dont see where else you're updating the value for the progress bar

[edit] .. why not take this

C#

for (int i = 1; i <= 100; i++)
{
  this.label1.Text += string.Format("{0}. This is a test.", i);
  Thread.Sleep(10000);
}

and make it this

C#

for (int i = 1; i <= 100; i++)
{
  this.label1.Text += string.Format("{0}. This is a test.", i);
  progressBar1.Value = i; 
  Thread.Sleep(10000);  // Not sure you need to delay for this long 
}

unless somehow Ive missed what your trying to do/what your problem is

[/edit]

Posted 31-Jul-16 18:39pm

Garth J Lancaster

Updated 31-Jul-16 20:09pm

v2

Comments

berrymaria 1-Aug-16 1:39am

Hi Sir Garth, I already updated my code.. Please help..

Garth J Lancaster 1-Aug-16 2:05am

you still dont update progressBar1.Value in the loop ! see the updated solution (in a minute after I've edited it)

berrymaria 1-Aug-16 2:06am

Yes Sir, i did not update the value of the progress bar because I just want to use the Marquee Style..

berrymaria 1-Aug-16 2:07am

I have encountered a new error Sir..

Garth J Lancaster 1-Aug-16 2:16am

you can handle that error by using BeginInvoke - see the strike through text and apply the same type of thing to label1.text

berrymaria 1-Aug-16 2:47am

I tried this Sir, as your advise..
label1.BeginInvoke(
new Action(() =>
{
for (int i = 1; i <= 1000; i++)
{
this.label1.Text += string.Format("{0}. This is a test.\n", i);

}
}
));
Thread.Sleep(10000);

Yes no error anymore. but my Progress Bar will freeze.. instead of displaying Marquee, while looping.. Please help.

Philippe Mori 1-Aug-16 10:59am

Obviously, if you send 1000 updates in a row, the UI will freeze during that time as those updates will arrive much faster than the UI would update!

To make it work, obviously the delay must be inside the loop (10ms each iteration instead of 10 seconds at once at the end).

Also, if generating data is much faster than updating the UI, then at some point, you need to skip displaying some items. Also, it would not make much sense to display dozen of values each seconds if you cannot read them...

Another point, is that it make no sense to put the loop in the Invoke call as you move back all processing to the UI thread defeating the purpose of using a background thread...