using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Reflection;

using System.Threading;

using System.Windows.Forms;

namespace BackgroundWorkerExplore

{

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        #region 异步处理

        //002

        private int RetrieveData(BackgroundWorker worker, DoWorkEventArgs e)

        {

            int max = (int)e.Argument;

            int percent = 0;

            for (int i = 1; i <= max; i++)

            {

                if (worker.CancellationPending) return i;

                percent = (int)(((double)i / (double)max) * 100);

                // 摘要:

                //     引发 System.ComponentModel.BackgroundWorker.ProgressChanged 事件。

                //   percentProgress:     已完成的后台操作所占的百分比，范围从 0% 到 100%。

                //   userState:/     传递到 System.ComponentModel.BackgroundWorker.RunWorkerAsync(System.Object) 的状态对象。

                worker.ReportProgress(percent, new KeyValuePair<int, string>(i, Guid.NewGuid().ToString()));

                Thread.Sleep(500);

            }

            return max;

        }

        //001 首先执行dowork

        private void bgworker_DoWork(object sender, DoWorkEventArgs e)

        {

            try

            {

                e.Result = RetrieveData(this.bgworker, e);

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message);

                throw;

            }

        }

        //003

        private void bgworker_ProgressChanged(object sender, ProgressChangedEventArgs e)

        {

            KeyValuePair<int, string> record = (KeyValuePair<int, string>)e.UserState;

            //操作UI

            this.labelResultLeft.Text = string.Format("There are {0} records retrieved!", record.Key);

            this.progressBarLeft.Value = e.ProgressPercentage;

            this.lvLeft.Items.Add(record.Value);

        }

        //004所有操作执行完后执行

        private void bgworker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

        {

            try

            {

                this.labelResultLeft.Text = string.Format("Total records: {0}", e.Result);

                this.btnStart.Enabled = true;

                this.btnStop.Enabled = false;

            }

            catch (TargetInvocationException ex)

            {

                MessageBox.Show(ex.InnerException.GetType().ToString());

            }

        }

        #endregion

        private void btnStart_Click(object sender, EventArgs e)

        {

            if (this.bgworker.IsBusy) return;

            this.lvLeft.Items.Clear();

            int MaxValue = 10;

            this.bgworker.RunWorkerAsync(MaxValue);

            this.btnStart.Enabled = false;

            this.btnStop.Enabled = true;

        }

        private void btnStop_Click(object sender, EventArgs e)

        {

            this.bgworker.CancelAsync();

        }

    }

}