该事件的RunWorkerCompletedEventArgs参数包含三个常用的属性Error,Cancelled,Result。其中，Error表示在执行异步操作期间发生的错误；Cancelled用于判断用户是否取消了异步操作；Result属性接收来自DoWork事件的DoWorkEventArgs参数的Result属性值，可用于传递异步操作的执行结果。
4、附源代码：
前台
后台
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace PrograssBar
{
public partial class PrograssBarUseBackgroundWorker : Form
{
private BackgroundWorker bgWorker = new BackgroundWorker();
public PrograssBarUseBackgroundWorker()
{
InitializeComponent();
InitializeBackgroundWorker();
}
private void InitializeBackgroundWorker()
{
bgWorker.WorkerReportsProgress = true;
bgWorker.WorkerSupportsCancellation = true;
bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
bgWorker.ProgressChanged += new ProgressChangedEventHandler(bgWorker_ProgessChanged);
bgWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgWorker_WorkerCompleted);
}
private void btnStart_Click(object sender, EventArgs e)
{
if (bgWorker.IsBusy)
return;
this.progressBar1.Maximum = 100;
this.btnStart.Enabled = false;
this.btnStop.Enabled = true;
bgWorker.RunWorkerAsync("hello");
}
public void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i <= 100; i++)
{
if (bgWorker.CancellationPending)
{
e.Cancel = true;
return;
}
else
{
bgWorker.ReportProgress(i,"Working");
System.Threading.Thread.Sleep(10);
}
}
}
public void bgWorker_ProgessChanged(object sender, ProgressChangedEventArgs e)
{
//string state = (string)e.UserState;//接收ReportProgress方法传递过来的userState
this.progressBar1.Value = e.ProgressPercentage;
this.label1.Text = "处理进度:" + Convert.ToString(e.ProgressPercentage) + "%";
}
public void bgWorker_WorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if(e.Error!=null)
{
MessageBox.Show(e.Error.ToString());
return;
}
if (!e.Cancelled)
this.label1.Text = "处理完毕!";
else
this.label1.Text = "处理终止!";
}
private void btnStop_Click(object sender, EventArgs e)
{
this.btnStart.Enabled = true;
this.btnStop.Enabled = false;
bgWorker.CancelAsync();
}
}
}
