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 = 100;
        }
        //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 % 10 == 0)
                textBox1.Text += "
" + value;
            else
                textBox1.Text += "-" + value;
            label1.Text = string.Format("完成{0}%", (value + 1) * 100 / 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 = 0; i < 100; 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(50);
            }
            return -1;
        }
        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: