本文转载自：https://www.cnblogs.com/zhaoshujie/p/9634136.html
查询了一下MSDN文档，其中微软就BackgroundWorker类的功能有这么一个描述（英文的，根据个人理解翻译）：BackgroundWorker类允许您在单独的线程上执行某个可能导致用户界面（UI）停止响应的耗时操作（比如文件下载数据库事务等），并且想要一个响应式的UI来反应当前耗时操作的进度。
可以看的出来，BackgroundWorker组件提供了一种执行异步操作（后台线程）的同时，并且还能妥妥的显示操作进度的解决方案。于是乎，我便深入的了解了一下BackgroundWorker类。针对BackgroundWorker类的部分重要属性和方法进行了一次总结。
private BackgroundWorker bgWorker = new BackgroundWorker(); bgWorker.WorkerReportsProgress = true;
bgWorker.WorkerSupportsCancellation = true;
//在DoWork中键入如下代码
for (int i = 0; i <= 100; i++)
{
if (bgWorker.CancellationPending)
{
e.Cancel = true;
return;
}
else
{
bgWorker.ReportProgress(i,"Working");
System.Threading.Thread.Sleep(10);
}
}
//防止重复执行异步操作引发错误
if (bgWorker.IsBusy)
return;
bgWorker.RunWorkerAsync();
//在启动异步操作的地方键入代码
bgWorker.RunWorkerAsync("hello");
for (int i = 0; i <= 100; i++)
{
//向ProgressChanged报告进度
bgWorker.ReportProgress(i,"Working");
System.Threading.Thread.Sleep(10);
}
//在需要执行取消操作的地方键入以下代码 bgWorker.CancelAsync();
DoWork
用于承载异步操作。当调用BackgroundWorker.RunWorkerAsync()时触发。
需要注意的是，由于DoWork事件内部的代码运行在非UI线程之上，所以在DoWork事件内部应避免于用户界面交互，而于用户界面交互的操作应放置在ProgressChanged和RunWorkerCompleted事件中。
ProgressChanged
当调用BackgroundWorker.ReportProgress(int percentProgress)方式时触发该事件。
该事件的ProgressChangedEventArgs.ProgressPercentage属性可以接收来自ReportProgress方法传递的percentProgress参数值,ProgressChangedEventArgs.UserState属性可以接收来自ReportProgress方法传递的userState参数。
RunWorkerCompleted
异步操作完成或取消时执行的操作，当调用DoWork事件执行完成时触发。
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。
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();
}
}
}
运行结果：
原文：https://www.cnblogs.com/hanguoshun/p/12871396.html
