Question

(Sorry for the not-so-good-title, I’m not sure how my problem can be solved, thus what is the question I need to ask 🙂

Context

I use a progress bar to inform the user of the progress of a task. The task is in fact done in two steps, each of them taking approximately half of the total time to be performed. I only know the length of the second task just before starting it (because it depends on the results of the previous task), so I can’t know the maximum progress at the very beginning. That is why I change the maximum progress of my progress bar before the second task.

This is basically how I do it:

// 1st step
progressBar.Maximum = step1Objects.Count * 2; // "2" because the step will take 
                                              // half of the total process
progressBar.Value = 0;
foreach (SomeObject step1Object in step1Objects) {
    // Build step2Objects
    progressBar.Value = ++progress;
}
// At this moment, the progress bar is half filled

// 2nd step
progressBar.Maximum = step2Objects.Count * 2;
progressBar.Value = step2Objects.Count;
// When we start this step, the progress bar is already half filled
foreach (SomeObject step2Object in step2Objects) {
    // Do something
    progressBar.Value = ++progress;
}
// At this moment, the progress bar is totally filled

Problem

When I get to this line:

progressBar.Maximum = step2Objects.Count * 2;

… the progress bar is for a short instant not half filled anymore because step1Objects.Count is very little compared to step2Objects.Count. So the progress bar does something like that (that’s what the user sees):

>          |
=>         |
==>        |
===>       |
====>      |
=====>     |  End of step 1
=>         |  progressBar.Maximum = step2Objects.Count * 2;
=====>     |  progressBar.Value = step2Objects.Count;
======>    |
=======>   |
========>  |
=========> |
==========>|

Question

How can I avoid this “glitch”?

I think that the thing to do is stop the refresh of the progress bar between the two steps. I was thinking at something like BeginUpdate/EndUpdate, but it doesn’t seem to exist for progress bars…

Answer 1

You write that both tasks are approximately half of the total time to be performed.

progressBar.Maximum = 100;

var stepPercentage = 50 / step1Objects.Count;
foreach(SomeObject step1Object in step1Objects)
{
    progressBar.Progress += stepPercentage;
}

progressBar.Progress = 50;
stepPercentage = 50 / step2Objects.Count;
foreach(SomeObject step2Object in step2Objects)
{
    progressBar.Progress += (stepPercentage + 50);
}