using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO;
using System.Threading;

namespace BackgroundWorkerDemo
{
    public partial class FrmDemo : Form
    {
        //設(shè)置生成臨時文件的路徑
        static string strSaveDir = @"F:\培訓";
        public FrmDemo()
        {
            InitializeComponent();

            //顯示后臺操作的執(zhí)行進度
            this.bgWork.WorkerReportsProgress = true;
            //可以取消后臺正在執(zhí)行的操作
            this.bgWork.WorkerSupportsCancellation = true;
        }

        /// <summary>
        /// 開始
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_Start_Click(object sender, EventArgs e)
        {
            if (Directory.Exists(strSaveDir) == false)
            {
                return;
            }
            btn_Start.Enabled = false;
            int count = Convert.ToInt32(this.txt_File.Text.ToString().Trim());
            //設(shè)置進度條
            this.proBar.Minimum = 0;
            this.proBar.Maximum = count;
            this.proBar.Value = this.proBar.Minimum;
            //開始執(zhí)行異步線程，進行后臺操作,給后臺傳遞參數(shù)
            this.bgWork.RunWorkerAsync(count);
        }

        /// <summary>
        /// 后臺操作要處理的任務(wù)代碼
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void bgWork_DoWork(object sender, DoWorkEventArgs e)
        {
            //獲取從RunWorkerAsync（）方法里面?zhèn)鬟f的參數(shù)的值
            int fileCount= Convert.ToInt32(e.Argument);
            Random rand = new Random();
            byte[] buffer = new byte[2048];
            for (int i = 0; i < fileCount; i++)
            {
                try
                {
                    string strFileName = Path.Combine(strSaveDir, i.ToString() + ".tmp");
                    using (var stream = File.Create(strFileName))
                    {
                        int n = 0;
                        int maxByte = 8 * 1024 * 1024;
                        while (n < maxByte)
                        {
                            rand.NextBytes(buffer);
                            stream.Write(buffer, 0, buffer.Length);
                            n += buffer.Length;
                        }
                    }
                }
                catch (Exception ex)
                {
                    continue;
                }
                finally
                {
                    //報告進度
                    this.bgWork.ReportProgress(i + 1);
                    Thread.Sleep(100);
                }

                //判斷是否取消了后臺操作
                if (bgWork.CancellationPending)
                {
                    e.Cancel = true;
                    return;
                }

                //設(shè)置返回值
                e.Result = 234;
            }
        }

        /// <summary>
        /// 更新前臺界面進度條
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void bgWork_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            //獲取異步任務(wù)的進度百分百
            int val = e.ProgressPercentage;
            this.label2.Text = string.Format("已經(jīng)生成{0}個文件", val);
            //進度條顯示當前進度
            this.proBar.Value = val;
        }

        /// <summary>
        /// 后臺操作完成，向前臺反饋信息
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void bgWork_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            btn_Start.Enabled = true;
            //用戶取消操作(e.Cancelled==true,表示異步操作已被取消)
            if (e.Cancelled)
            {
                MessageBox.Show("用戶取消后臺操作", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("操作完成", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                //接收返回值
                int result = (int)e.Result;

                MessageBox.Show("返回值:" + result);
            }
        }

        /// <summary>
        /// 取消
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btn_Cancle_Click(object sender, EventArgs e)
        {
            //調(diào)用CancelAsync（），取消掛起的后臺操作
            this.bgWork.CancelAsync();
        }
    }
}