查找文件时的ProgressBar

Question

Hi I am trying to show a progress bar while in background the code is looping till it finds a file with specific name.

I have written following code for that but the progress bar values doesn't change.

What should I change in the code below?

public partial class Form1 : Form
{
    BackgroundWorker backgroundWorker1 = new BackgroundWorker();  
    public Form1()
    {
        InitializeComponent();
        progressBar1.Visible = false;
        backgroundWorker1.WorkerReportsProgress = true;

        backgroundWorker1.DoWork +=
            new DoWorkEventHandler(backgroundWorker1_DoWork);
        backgroundWorker1.ProgressChanged +=
            new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
        backgroundWorker1.RunWorkerCompleted +=
            new RunWorkerCompletedEventHandler(backgroundWorker1_WorkDone);

    }

    private void button1_Click(object sender, EventArgs e)
    {
        backgroundWorker1.RunWorkerAsync();
        progressBar1.Visible = true;
    }

    void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        // Your background task goes here
        for (int i = 0; i <= 100; i++)
        {
            // Report progress to 'UI' thread
            backgroundWorker1.ReportProgress(i);
            // Simulate long task


            while (!File.Exists(@"C:\Users\Test.txt"))
            {
                continue;
            }
        }
    }

    void backgroundWorker1_ProgressChanged(object sender,
        ProgressChangedEventArgs e)
    {
        // The progress percentage is a property of e
        progressBar1.Value = e.ProgressPercentage;
    }

    void backgroundWorker1_WorkDone(object sender,
        RunWorkerCompletedEventArgs e)
    {
        progressBar1.Visible = false;
    }
}

Answer 1

The continue in your code will simply continue to the next iteration of the while(true) loop. It won't go back up to the for loop as you expect - it just keeps looping in there over and over again. If it wasn't a background worker, it'd hang your entire program. Since it is, it just hangs that thread. I expect that one CPU core stays at 100% while this is running.

That being said, while the goal here is admirable, there's no good way to accomplish it. Even if you fix the infinite loop, your progress bar will either "finish" at a low percentage (1%, 2%, 3%, done) or go up to 100, then stop updating, but without the file yet existing.