BackgroundWorker学习

后台代码：

 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();
         }
     }
 }

页面效果: