Question

Im trying to update a progress bar while doing some data type checks on a separate thread and there seems to be a delay between what value the progress bar is at and the value which is actually show.

The following code is executed by the non-GUI thread and is used to raise the event.

    protected virtual void OnUpdateProgressBar(object sender, ProgressBarEventArgs e)
    {
        EventHandler<ProgressBarEventArgs> TempHandler = UpdateProgressBar;

        //Avoid possible race condition.
        if (TempHandler != null)
        {
            TempHandler(this, e);
        }
    }

I have created a separate class for updating the progress bar and when i create an instance of it, i pass a reference to the progress bar. Below is the entire class.

public class ProgressBarChanged
{
    ProgressBar statusBar;

    public ProgressBarChanged(ProgressBar pb)
    {
        statusBar = pb;
        statusBar.Value = 0;
    }
    public ProgressBarChanged()
    {
    }

    public void subscribeToEvent(DataVerification test)
    {
        test.UpdateProgressBar += new EventHandler<ProgressBarEventArgs>(incrementPB);
    }

    public void incrementPB(object sender, ProgressBarEventArgs e)
    {
        Action action = () =>
        {
            if (e.CurrentRow == e.FinalRow - 10)
            {
                int i = 5;
            }
            statusBar.Maximum = e.FinalRow;
            statusBar.Value = e.CurrentRow;
        };

        if(statusBar.InvokeRequired)
           statusBar.Invoke(action);
        else
            action();
    }
}

I have uploaded a screen shot showing the progress bar and the actual values.
Any ideas???

Thanks

Answer 1

The progessbar is a simple feedback to the user, not a piece of exact instrumentation. It’s a pacifier.

It also incorporates it’s own async logic to update the screen (independent of the message loop). This makes that it may run a little behind.

What’s the big deal?

To get more accurate results, divide your range into < 100 segments and do fewer updates.