浅谈.Net异步编程的前世今生----EAP篇

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

namespace BackgroundWorkerDemo
{
    public partial class BackgroundWorkerForm : Form
    {
        public BackgroundWorkerForm()
        {
            InitializeComponent();
            backgroundWorker1.WorkerReportsProgress = true;
            backgroundWorker1.WorkerSupportsCancellation = true;
        }

        /// <summary>
        /// 点击开始下载按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnDownLoad_Click(object sender, EventArgs e)
        {
            if (!backgroundWorker1.IsBusy) //判断是否正在执行异步操作
            {
                //backgroundWorker开始执行异步操作
                backgroundWorker1.RunWorkerAsync();
            }
        }

        /// <summary>
        /// 点击取消按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnCancel_Click(object sender, EventArgs e)
        {
            if (backgroundWorker1.WorkerSupportsCancellation) //判断是否支持异步取消操作
            {
                //开始执行取消操作
                backgroundWorker1.CancelAsync();
            }
        }

        /// <summary>
        /// backgroundworker异步执行事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            System.ComponentModel.BackgroundWorker worker = sender as System.ComponentModel.BackgroundWorker;
            string msg = "当前线程是否为后台线程：" + Thread.CurrentThread.IsBackground + "，是否为线程池线程：" + Thread.CurrentThread.IsThreadPoolThread;
            WriteLog("Backgroundworker日志", msg);
            for (int i = 0; i < 20; i++)
            {
                if (worker.CancellationPending)
                {
                    e.Cancel = true;
                    break;
                }
                else
                {
                    //模拟下载执行进度
                    Thread.Sleep(500);
                    worker.ReportProgress(i * 5);
                }
            }
        }

        /// <summary>
        /// 进度报告事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            lblProcess.Text = "当前下载进度为：" + e.ProgressPercentage + "%，是否为后台线程：" + Thread.CurrentThread.IsBackground 
+ "，是否为线程池线程：" + Thread.CurrentThread.IsThreadPoolThread;
        }

        /// <summary>
        /// 异步操作完成事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled) //此状态为取消
            {
                lblProcess.Text = "下载已经被取消";
            }
            else if (e.Error != null)
            {
                lblProcess.Text = "出现错误：" + e.Error.Message;
            }
            else
            {
                lblProcess.Text = "下载已完成";
            }
        }

        /// <summary>
        /// 记录日志
        /// </summary>
        /// <param name="documentName"></param>
        /// <param name="msg"></param>
        public void WriteLog(string documentName, string msg)
        {
            string errorLogFilePath = System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Log");
            if (!System.IO.Directory.Exists(errorLogFilePath))
            {
                System.IO.Directory.CreateDirectory(errorLogFilePath);
            }
            string logFile = System.IO.Path.Combine(errorLogFilePath, documentName + "@" + DateTime.Today.ToString("yyyy-MM-dd") + ".txt");
            bool writeBaseInfo = System.IO.File.Exists(logFile);
            StreamWriter swLogFile = new StreamWriter(logFile, true, Encoding.Unicode);
            swLogFile.WriteLine(DateTime.Now.ToString("HH:mm:ss") + "\t" + msg);
            swLogFile.Close();
            swLogFile.Dispose();
        }  
    }
}