使用 BackgroundWorker 完成任務

以下示例演示如何使用 BackgroundWorker 更新 WinForms ProgressBar。backgroundWorker 將在不阻止 UI 執行緒的情況下更新進度條的值，從而在後臺完成工作時顯示響應式 UI。

namespace BgWorkerExample
{
    public partial class Form1 : Form
{

    //a new instance of a backgroundWorker is created.
    BackgroundWorker bgWorker = new BackgroundWorker();
    
    public Form1()
    {
        InitializeComponent();

        prgProgressBar.Step = 1;

        //this assigns event handlers for the backgroundWorker
        bgWorker.DoWork += bgWorker_DoWork;
        bgWorker.RunWorkerCompleted += bgWorker_WorkComplete;

        //tell the backgroundWorker to raise the "DoWork" event, thus starting it.
        //Check to make sure the background worker is not already running.
        if(!bgWorker.IsBusy)
            bgWorker.RunWorkerAsync();
        
    }

    private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        //this is the method that the backgroundworker will perform on in the background thread.
        /* One thing to note! A try catch is not necessary as any exceptions will terminate the backgroundWorker and report 
          the error to the "RunWorkerCompleted" event */
        CountToY();    
    }

    private void bgWorker_WorkComplete(object sender, RunWorkerCompletedEventArgs e)
    {
        //e.Error will contain any exceptions caught by the backgroundWorker
        if (e.Error != null)
        {
            MessageBox.Show(e.Error.Message);
        }
        else
        {
            MessageBox.Show("Task Complete!");
            prgProgressBar.Value = 0;
        }
    }

    // example method to perform a "long" running task.
    private void CountToY()
    {
        int x = 0;

        int maxProgress = 100;
        prgProgressBar.Maximum = maxProgress;
        

        while (x < maxProgress)
        {
            System.Threading.Thread.Sleep(50);
            Invoke(new Action(() => { prgProgressBar.PerformStep(); }));
            x += 1;
        }
    }

}

結果如下……