C#多线程BackgroundWorker使用示例

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

namespace BackgroundWorkerSample
{
    public partial class CalculateAddForm : Form
    {
        protected BackgroundWorker backgroundWorker1 = new BackgroundWorker();
        //private int numberToCompute = 0;
        //private int highestPercentageReached = 0;

        public CalculateAddForm()
        {
            InitializeComponent();

            InitializeBackgoundWorker();
           
        }

        // Set up the BackgroundWorker object by
        // attaching event handlers.
        private void InitializeBackgoundWorker()
        {
            this.backgroundWorker1.WorkerReportsProgress = true;
            this.backgroundWorker1.WorkerSupportsCancellation = true;
           
            this.backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
            this.backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
            this.backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
        }

        private long ComputeAdd(int n, BackgroundWorker worker, DoWorkEventArgs e)
        {
            long result = 0;

            // Abort the operation if the user has canceled.
            // Note that a call to CancelAsync may have set
            // CancellationPending to true just after the
            // last invocation of this method exits, so this
            // code will not have the opportunity to set the
            // DoWorkEventArgs.Cancel flag to true. This means
            // that RunWorkerCompletedEventArgs.Cancelled will
            // not be set to true in your RunWorkerCompleted
            // event handler. This is a race condition.

            for (int i = 1; i <= n; i++)
            {
                if (worker.CancellationPending)
                {
                    e.Cancel = true;
                    break;
                }
                else
                {
                    result += i;
                    Thread.Sleep(100);
                    // Report progress as a percentage of the total task.
                    int percentComplete = (int)((float)i / (float)n * 100);
                    worker.ReportProgress(percentComplete);
                }
            }
            return result;
        }
       
        void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            // Get the BackgroundWorker that raised this event.
            BackgroundWorker worker = sender as BackgroundWorker;

            // Assign the result of the computation
            // to the Result property of the DoWorkEventArgs
            // object. This is will be available to the
            // RunWorkerCompleted eventhandler.
            e.Result = ComputeAdd((int)e.Argument, worker, e);
           
            // If the operation was canceled by the user,
            // set the DoWorkEventArgs.Cancel property to true.
            if (worker.CancellationPending)
            {
                e.Cancel = true;
            }
        }

        void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            this.progressBar1.Value = e.ProgressPercentage;
        }

        void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            // First, handle the case where an exception was thrown.
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
            }
            else if (e.Cancelled)
            {
                // Next, handle the case where the user canceled
                // the operation.
                // Note that due to a race condition in
                // the DoWork event handler, the Cancelled
                // flag may not have been set, even though
                // CancelAsync was called.
                resultLabel.Text = "Canceled";
            }
            else
            {
                // Finally, handle the case where the operation
                // succeeded.
                resultLabel.Text = e.Result.ToString();
            }

            // Enable the UpDown control.
            this.numericUpDown1.Enabled = true;

            // Enable the Start button.
            startAsyncButton.Enabled = true;

            // Disable the Cancel button.
            cancelAsyncButton.Enabled = false;

        }

       
        private void startAsyncButton_Click(object sender, EventArgs e)
        {
            // Reset the text in the result label.
            resultLabel.Text = String.Empty;

            // Disable the UpDown control until
            // the asynchronous operation is done.
            this.numericUpDown1.Enabled = false;

            // Disable the Start button until
            // the asynchronous operation is done.
            this.startAsyncButton.Enabled = false;

            // Enable the Cancel button while
            // the asynchronous operation runs.
            this.cancelAsyncButton.Enabled = true;

            // Get the value from the UpDown control.
            int numberToCompute = (int)numericUpDown1.Value;

            // Reset the variable for percentage tracking.
            //highestPercentageReached = 0;

            // Start the asynchronous operation.
            backgroundWorker1.RunWorkerAsync(numberToCompute);

        }

        private void cancelAsyncButton_Click(object sender, EventArgs e)
        {
            // Cancel the asynchronous operation.
            this.backgroundWorker1.CancelAsync();

            // Disable the Cancel button.
            cancelAsyncButton.Enabled = false;

        }       
    }
}