dotneat.net

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

namespace BackgroundWorker
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            //mandatory. Otherwise will throw an exception when calling ReportProgress method
            backgroundWorker1.WorkerReportsProgress = true; 

            //mandatory. Otherwise we would get an InvalidOperationException when trying to cancel the operation
            backgroundWorker1.WorkerSupportsCancellation = true;
        }



        //This method is executed in a separate thread created by the background worker.
        //so don't try to access any UI controls here!! (unless you use a delegate to do it)
        //this attribute will prevent the debugger to stop here if any exception is raised.
        //[System.Diagnostics.DebuggerNonUserCodeAttribute()]
        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            //NOTE: we shouldn't use a try catch block here (unless you rethrow the exception)
            //the backgroundworker will be able to detect any exception on this code.
            //if any exception is produced, it will be available to you on 
            //the RunWorkerCompletedEventArgs object, method backgroundWorker1_RunWorkerCompleted
            //try
            //{
                DateTime start = DateTime.Now;
                e.Result = "";
                for (int i = 0; i < 100; i++)
                {
                    System.Threading.Thread.Sleep(50); //do some intense task here.
                    backgroundWorker1.ReportProgress(i, DateTime.Now); //notify progress to main thread. We also pass time information in UserState to cover this property in the example.
                    //Error handling: uncomment this code if you want to test how an exception is handled by the background worker.
                    //also uncomment the mentioned attribute above to it doesn't stop in the debugger.
                    //if (i == 34)
                    //    throw new Exception("something wrong here!!");

                    //if cancellation is pending, cancel work.
                    if (backgroundWorker1.CancellationPending)
                    {
                        e.Cancel = true; 
                        return;
                    }
                }

                TimeSpan duration = DateTime.Now - start;
                
                //we could return some useful information here, like calculation output, number of items affected, etc.. to the main thread.
                e.Result = "Duration: " + duration.TotalMilliseconds.ToString() + " ms.";
            //}
            //catch(Exception ex){
            //    MessageBox.Show("Don't use try catch here, let the backgroundworker handle it for you!");
            //}
        }


        
        //This event is raised on the main thread.
        //It is safe to access UI controls here.
        private void backgroundWorker1_ProgressChanged(object sender, 
            ProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage; //update progress bar
            
            DateTime time = Convert.ToDateTime(e.UserState); //get additional information about progress
            
            //in this example, we log that optional additional info to textbox
            txtOutput.AppendText(time.ToLongTimeString());
            txtOutput.AppendText(Environment.NewLine);            
        }



        //This is executed after the task is complete whatever the task has completed: a) sucessfully, b) with error c)has been cancelled
        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 btoCancel_Click(object sender, EventArgs e)
        {
            //notify background worker we want to cancel the operation.
            //this code doesn't actually cancel or kill the thread that is executing the job.
            backgroundWorker1.CancelAsync();
        }

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

      
    }
}

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