C# 为什么赢了'；打印消息不是用我的C代码打印的吗？

我正在尝试在循环运行之前将消息“printing…”打印到txtMessage.Text文本框，但在循环运行之前，它从未打印到文本框。知道为什么吗

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!";
            }

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设置文本后，尝试添加刷新调用。有可能您进入循环的速度足够快，只有退出才能刷新

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!";
}

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您的代码在单个线程中运行。您应该将文本设置为“打印…”，然后旋转一个新线程来执行循环卡纸

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请查看问题和前3个答案。

Lol。您自己用“completed！”消息重写了它。@Jk要进一步扩展，无论您在哪里使用

txtMessage.Text=…

，您都应该将其更改为

txtMessage.Text+=…

，除非您只想显示新的内容message@JK. 是的，它的罚款覆盖后，为loop@Rob即使我将其添加到if和else语句之前，它仍然不会在for循环之前打印。Winform不会及时更新UI线程-这就是为什么作业已完成的原因。不过，您会注意到，在“打印”时，您的UI仍然会被冻结。点击打印并尝试移动或调整窗体大小。