C# Winform ProgressBar and BackgroundWorker

Question

I have the following problem:

I have a Form named MainForm. I have a long operation to be taken place on this form.

While this long operation is going on, I need to show another from named ProgressForm on top of the MainForm.

ProgressForm contains a progress bar which needs to be updated while the long operation is taking place.

After the long operation is completed, the ProgressForm should be closed automatically.

I have written the following code:

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace ClassLibrary
{
    public class MyClass
    {
        public static string LongOperation()
        {
            Thread.Sleep(new TimeSpan(0,0,30));

            return "HelloWorld";
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace BackgroungWorker__HelloWorld
{
    public partial class ProgressForm : Form
    {
        public ProgressForm()
        {
            InitializeComponent();
        }

        public ProgressBar ProgressBar
        {
            get { return this.progressBar1; }
            set { this.progressBar1 = value; }
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

using ClassLibrary;

namespace BackgroungWorker__HelloWorld
{
    public partial class MainForm : Form
    {
        ProgressForm f = new ProgressForm();

        public MainForm()
        {
            InitializeComponent();  
        }

        int count = 0;
        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            if (f != null)
            {
                f.ProgressBar.Value = e.ProgressPercentage;
            }

            ++count;
        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled) 
            {  
                MessageBox.Show("The task has been cancelled");  
            }  
            else if (e.Error != null)  
            {                  
                MessageBox.Show("Error. Details: " + (e.Error as Exception).ToString());  
            }  
            else 
            {  
                MessageBox.Show("The task has been completed. Results: " + e.Result.ToString());  
            }
        }


        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            if (f == null)
            {
                f = new ProgressForm();
            }

            f.ShowDialog();

            //backgroundWorker1.ReportProgress(100);

            MyClass.LongOperation();

            f.Close();
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            backgroundWorker1.RunWorkerAsync();
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            backgroundWorker1.CancelAsync();

            this.Close();
        }
    }
}

I can't find a way to update the progressBar.

Where should I place backgroundWorker1.ReportProgress() and how should I call this?

I must not make any change in MyClass because I don't know what would happen or how long it takes to complete the operation in this layer of my application.

Can anyone help me?

Answer 1

One problem is that you're sleeping for 30 seconds. Normally you'd call ReportProgress at various points within your long-running task. So to demonstrate this, you might want to change your code to sleep for 1 second, but 30 times - calling ReportProgress each time it finishes a sleep.

Another problem is that you're showing your ProgressForm from the background thread. You should start it in the UI thread, but hook the background worker's ProgressChanged event to it. Then when the background worker reports progress, the progress form will be updated.