Why won't the printing message print in my C# code?

Question

I am trying to print out the message "printing..." to the txtMessage.Text text box before the loop runs but it never does print to the text box before the loop runs. Any idea why?

else
            {
                txtMessage.Text = "Printing...";
                for (int i = numberCopies; i != 0; i--)
                {
                    int paper = Convert.ToInt32(lblPaperAmount.Text);
                    paper--;
                    if (paper == 480 || paper == 380 || paper == 400 || paper == 200)
                    {
                        MessageBox.Show("There is a paper Jam! Please remove the Jam and then hit the ok button to continue!", "Important Message", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

                    }
                    lblPaperAmount.Text = Convert.ToString(Convert.ToInt32(lblPaperAmount.Text) - 1);
                    lblTonerAmount.Text = Convert.ToString(Convert.ToInt32(lblTonerAmount.Text) - 1);
                    Thread.Sleep(1000);
                }
                txtMessage.Text = "Job is completed!";
            }

Lol. You overwrote it yourself with the "completed!" message. — JK., Jul 23 '15 at 23:11
@Jk To expand on that, wherever you use `txtMessage.Text = ...`, you should change it to `txtMessage.Text += ...`, unless you want show *only* the new message — Rob, Jul 23 '15 at 23:14
@Rob Even if i add it before the if and else statement it still wont print before the for loop. — tstokes8040, Jul 23 '15 at 23:18
Winform does not update the UI thread in time - that is why Job is Completed is all you see. — juanvan, Jul 23 '15 at 23:20
@Blorgbeard What do you recommend me use then? I want to basically slow the rate of the for loop so it acts more like a printer :). — tstokes8040, Jul 24 '15 at 00:09
`BackgroundWorker` to do the printing logic with `ReportProgress` to update the form or send error messages back. — Blorgbeard, Jul 24 '15 at 00:12

score 2 · Accepted Answer · answered Jul 23 '15 at 23:23

Try adding a call to Refresh after setting the text. It's possible you're entering the loop quickly enough the refresh does not happen until you exit.

else
{
    txtMessage.Text = "Printing...";
    txtMessage.Refresh(); //force the control to redraw
    for (int i = numberCopies; i != 0; i--)
    {
        int paper = Convert.ToInt32(lblPaperAmount.Text);
        paper--;
        if (paper == 480 || paper == 380 || paper == 400 || paper == 200)
        {
            MessageBox.Show("There is a paper Jam! Please remove the Jam and then hit the ok button to continue!", "Important Message", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);

        }
        lblPaperAmount.Text = Convert.ToString(Convert.ToInt32(lblPaperAmount.Text) - 1);
        lblTonerAmount.Text = Convert.ToString(Convert.ToInt32(lblTonerAmount.Text) - 1);
        Thread.Sleep(1000);
    }
    txtMessage.Text = "Job is completed!";
}

You'll notice that your UI will still be frozen while "printing" though. Hit print and try to move or resize the form. — Blorgbeard, Jul 24 '15 at 00:11

score 0 · Answer 2 · edited May 23 '17 at 11:58

0

Your code is running in a single thread. You should set your text to "Printing..." then spin off a new thread to do your paper jam for loop.

Please see this question and the top 3 answers.

edited May 23 '17 at 11:58

Community

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answered Jul 23 '15 at 23:24

Biff MaGriff

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Why won't the printing message print in my C# code?

2 Answers2