System.ComponentModel.BackgroundWorker在WinForm中的異步使用

爲了防止操作過程中界面卡死，和WinForm搭配最適合的就是BackgroundWorker了。BackgroundWorker 類

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace ProcessImpactID
{
    public partial class Form1 : Form
    {
        BackgroundWorker worker = new BackgroundWorker();

        public Form1()
        {
            InitializeComponent();

            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
            worker.ProgressChanged += Worker_ProgressChanged;
            //set it to true for support cancel event
            //when call CancelAsync() it can set property CancellationPending to true.
            worker.WorkerSupportsCancellation = true;
            //set it to true for raise Progress Report.
            worker.WorkerReportsProgress = true;
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            if (worker.IsBusy)
            {
                MessageBox.Show("the process has been started");
                return;
            }
            worker.RunWorkerAsync("e.argument");
        }

        private void btnStop_Click(object sender, EventArgs e)
        {
            if (worker.IsBusy)
            {
                worker.CancelAsync();
            }
        }

        private void Worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            //this is UI Thread
            this.label1.Text = e.ProgressPercentage.ToString();
        }

        void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            //bool isThreadPoolThread = System.Threading.Thread.CurrentThread.IsThreadPoolThread;
            //this is UI Thread
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message, "Error");
                return;
            }
            if (e.Cancelled)
            {
                MessageBox.Show("the process has been cancelled");
                return;
            }
            MessageBox.Show(e.Result.ToString());
        }

        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            //bool isThreadPoolThread = System.Threading.Thread.CurrentThread.IsThreadPoolThread;
            string str = (string)e.Argument;
            string result = "work result";
            worker.ReportProgress(0);
            for (int i = 0; i < 100; i++)
            {
                //if CancellationPending is true, stop process.
                //and report process result.
                if (worker.CancellationPending)
                {
                    e.Cancel = true;
                    break;
                }
                Thread.Sleep(1000);
                //Report Progress
                worker.ReportProgress(i * 1);
            }

            //set the RunWorkerCompleted result
            e.Result = string.Format("{0} => {1}", str, result);
        }
    }
}