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;

 namespace winform

 {

     public partial class fm : Form

     {

         BackgroundWorker worker;

         public fm()

         {

             InitializeComponent();

             worker = new BackgroundWorker();

             worker.WorkerReportsProgress = true;

             worker.WorkerSupportsCancellation = true;

             //正式做事情的地方

             worker.DoWork += new DoWorkEventHandler(DoWork);

             //任务完称时要做的，比如提示等等

             worker.ProgressChanged += new ProgressChangedEventHandler(ProgessChanged);

             //任务进行时，报告进度

             worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(RunWorkerCompleted);

             progressBar1.Maximum = ;

         }

         //调用 RunWorkerAsync 时发生

         public void DoWork(object sender, DoWorkEventArgs e)

         {

             e.Result = ComputeFibonacci(worker, e);

             //获取异步操作结果的值，当ComputeFibonacci(worker, e)返回时，异步过程结束

         }

         //调用 ReportProgress 时发生

         public void ProgessChanged(object sender, ProgressChangedEventArgs e)

         {

             this.progressBar1.Value = e.ProgressPercentage;

             //将异步任务进度的百分比赋给进度条

             int value = int.Parse(e.UserState.ToString());

             if (value %  == )

                 textBox1.Text += "\r\n" + value;

             else

                 textBox1.Text += "-" + value;

             label1.Text = string.Format("完成{0}%", (value + ) *  / progressBar1.Maximum);

         }

         //当后台操作已完成、被取消或引发异常时发生

         public void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

         {

             if (e.Cancelled)

                 MessageBox.Show("取消了");

             else

                 MessageBox.Show("完成！" + e.Result);

         }

         private int ComputeFibonacci(object sender, DoWorkEventArgs e)

         {

             for (int i = ; i < ; i++)

             {

                 //判断应用程序是否取消后台操作

                 if (worker.CancellationPending)

                 {

                     e.Cancel = true;

                     break;

                 }

                 //dowork function

                 worker.ReportProgress(i, i);

                 System.Threading.Thread.Sleep();

             }

             return -;

         }

         private void btnStart_Click(object sender, EventArgs e)

         {

             if (worker.IsBusy)

             {

                 MessageBox.Show("已经执行异步操作");

                 return;

             }

             textBox1.Text = "";

             label1.Text = "";

             worker.RunWorkerAsync();

             btnStart.Enabled = false;

             btnPause.Enabled = true;

         }

         private void btnPause_Click(object sender, EventArgs e)

         {

             btnPause.Enabled = false;

             btnStart.Enabled = true;

             worker.CancelAsync();

         }

     }

 }