使用控件 BackgroundWorker 的实质是为该进程新创建一个线程来执行耗时操作。

bool changed = false;private void tabControl1_Selected(object sender, TabControlEventArgs e){    changed = true;    if (!backgroundWorker1.IsBusy)    {        if (changed)        {            backgroundWorker1.RunWorkerAsync();        }    }}private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e){    // time-consuming operations    int sum = 0;    for (int i = 0; i < int.MaxValue; i++)    {        sum += i;    }    textBox1.Text = sum.ToString();    // time-consuming operations    changed = false;}

与直接创建一个线程相比，BackgroundWorker 不需要忽视控件多线程的安全机制，详见。

还可以使用 BackgroundWorker 异步创建新的窗口：

private void Open_Click(object sender, EventArgs e){    this.backgroundWorker1.RunWorkerAsync();}private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e){    ExternalForm ef = new ExternalForm();    ef.ShowDialog();}