BackgroundWorker是微软的在.net Framwork中添加的一个组件，主要对线程的访问提供了一种安全的方式。简单的说就是对Thread的一次封装。
BackgroundWorker位于System.ComponentModel下，是一个继承了Component的组件，微软官方的解释为：Executes an operation on a separate thread.就是说，开始一个新的线程执行操作。
首先介绍一下BackgroundWorker的相关属性和方法：
属性：
WorkerReportsProgress：是否可以报告进度。
WorkerSupportsCancellation：是否允许异步中止。
IsBusy：是否在运行。
CancellationPending：判断BackgroundWorker是否已经异步取消。
方法：
RunWorkerAsync：开始执行任务。触发DoWork事件
ReportProgress：异步提醒，触发ProgressChanged事件，但是这个如果可以使用，必须设置WorkerReportsProgress为True
CancelAsync：取消BackgroundWorker操作。
事件：
DoWork：执行RunWorkerAsync后触发，异步执行的认为。
ProgressChanged：执行ReportProgress时触发，异步获得进度。
RunWorkerCompleted：线程结束时触发，主要有成功结束，发生异常或者取消时发生。
Thread相对来说就简单了，但是使用起来就比较麻烦了。Thread位于System.Threading的名空间下，是一个可以独立创建和操作一个线程，并且对线程进行设置优先级和获得状态的一个不可继承的类。
下面是我做的一个例子，来比较他们两个的使用。
建立一个窗体，放置了两个TextBox，分别为设置开始和结束的Progree的值，放置两个ProgressBar，分别设置为线程的Progressbar和BackGroundWorker的ProgressBar。另外放置按钮为StartBackGroundWorker，StartThread，CancelBackGroundWorker，CancelThread和PauseThread。
BackGroundWorker的使用就非常简单：
/// <summary> /// Handles the Click event of the btnBackGroundWorker control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param> private void btnBackGroundWorker_Click(object sender, EventArgs e) { StartFrom = Convert.ToInt32(txtStart.Text); EndTo = Convert.ToInt32(txtEnd.Text); progressBarThread.Minimum = StartFrom; progressBarThread.Maximum = EndTo; this.btnBackGroundWorker.Enabled = false; this.backgroundWorker.RunWorkerAsync(); } /// <summary> /// Handles the DoWork event of the backgroundWorker control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.ComponentModel.DoWorkEventArgs"/> instance containing the event data.</param> private void backgroundWorker_DoWork(object sender, DoWorkEventArgs e) { for (int nValue = StartFrom; nValue <= EndTo; nValue++) { if (this.backgroundWorker.CancellationPending) { e.Cancel = true; return; } this.backgroundWorker.ReportProgress(nValue); Thread.Sleep(200); } } /// <summary> /// Handles the ProgressChanged event of the backgroundWorker control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.ComponentModel.ProgressChangedEventArgs"/> instance containing the event data.</param> private void backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e) { this.prgProcessBackGroundWorker.Value = e.ProgressPercentage; } /// <summary> /// Handles the RunWorkerCompleted event of the backgroundWorker control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.ComponentModel.RunWorkerCompletedEventArgs"/> instance containing the event data.</param> private void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) { // 取消 if (e.Cancelled) { MessageBox.Show("Cancelled"); } // 出现错误 else if (e.Error != null) { MessageBox.Show(e.Error.Message + Environment.NewLine + e.Error.StackTrace); } // 完成 else { MessageBox.Show("Completed"); this.btnBackGroundWorker.Enabled = true; } } /// <summary> /// Handles the Click event of the btnCancelBackgroundWoker control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param> private void btnCancelBackgroundWoker_Click(object sender, EventArgs e) { this.backgroundWorker.CancelAsync(); }
Thread的使用就比较麻烦了，对于尤其是对异步提醒来说，需要写委托，代码量是很多，但是对于BackgroundWorker来说，却没有线程暂停和继续的方法。但是对于一般的来说，这些功能也是不用的，而且在微软的文档中还提到了，Thread的Resume和Suspend已经不推荐使用。
// 声明委托 delegate void DelegateType(int x); DelegateType TheDelegate; // ProgressBar的开始和结束值 int StartFrom, EndTo; // 是否线程暂停 bool IsThreadPaused; ManualResetEvent CancelEvent = new ManualResetEvent(false); Thread MyThread; /// <summary> /// 委托的消息事件 /// </summary> /// <param name="nProgress">进度值</param> private void MessageHandler(int nProgress) { lblThreadStatus.Text = "处理: " + Convert.ToString(nProgress); progressBarThread.Value = nProgress; if (nProgress == progressBarThread.Maximum) { MessageBox.Show("Completed"); this.btnTread.Enabled = true; } } /// <summary> /// Handles the Click event of the btnTread control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param> private void btnTread_Click(object sender, EventArgs e) { TheDelegate = MessageHandler; StartFrom = Convert.ToInt32(txtStart.Text); EndTo = Convert.ToInt32(txtEnd.Text); progressBarThread.Minimum = StartFrom; progressBarThread.Maximum = EndTo; btnTread.Enabled = false; IsThreadPaused = false; MyThread = new Thread(ProcessRoutine); MyThread.Start(); } /// <summary> /// Processes the routine. /// </summary> private void ProcessRoutine() { for (int nValue = StartFrom; nValue <= EndTo; nValue++) { // 判断是否取消 if (CancelEvent.WaitOne(0, false) == true) { return; } this.BeginInvoke(this.TheDelegate, nValue); Thread.Sleep(200); } } /// <summary> /// Handles the Click event of the btnCancelThread control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param> private void btnCancelThread_Click(object sender, EventArgs e) { btnCancelThread.Enabled = false; btnPauseThread.Enabled = false; CancelEvent.Set(); MyThread.Join(); } /// <summary> /// Handles the Click event of the btnPauseThread control. /// </summary> /// <param name="sender">The source of the event.</param> /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param> private void btnPauseThread_Click(object sender, EventArgs e) { // Bad approach! if (!IsThreadPaused) { IsThreadPaused = true; MyThread.Suspend(); btnPauseThread.Text = "Resume Thread"; // Disallow Cancel btnCancelThread.Enabled = false; } else { IsThreadPaused = false; MyThread.Resume(); btnPauseThread.Text = "Pause Thread"; btnCancelThread.Enabled = true; } }
比较起来，两个是完全相同的，对于Thread来说，灵活性就比较好了，BackgroundWorker的使用就相对来说简单了。
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