标签：
本文介绍了BackgroundWorker组件的功能及在基于事件的异步操作编程中的应用，并对组件的实现原理进行简述。在应用程序中，可能会遇到一些执行耗时的功能操作，比如数据下载、复杂计算及数据库事务等，一般这样的功能会在单独的线程上实现，执行结束后结果显示到用户界面上，这样可避免造成用户界面长时间无响应情况。在.NET 2.0及以后的版本中，FCL提供了BackgroundWorker组件来方便的实现这些功能要求。
|
publicvoidRunWorkerAsync();
publicvoidRunWorkerAsync(Object argument);
|
|
publicvoid CancelAsync();
|
|
publicvoidReportProgress(int percentProgress);
publicvoidReportProgress(int percentProgress,Object userState);
|
|
publicboolCancellationPending { get; }
publicboolWorkerReportsProgress { get; set; }
publicboolWorkerSupportsCancellation { get; set; }
|
|
publicbool IsBusy { get; }
|
|
publiceventDoWorkEventHandler DoWork;
publiceventProgressChangedEventHandler ProgressChanged;
publiceventRunWorkerCompletedEventHandler RunWorkerCompleted;
|
|
private System.ComponentModel.BackgroundWorker backgroundWorker1;
private void InitializeBackgoundWorker()
{
this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
this.backgroundWorker1.WorkerReportsProgress = true;
this.backgroundWorker1.WorkerSupportsCancellation = true;
this.backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
this.backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
this.backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
}
|
|
private void startAsyncButton_Click(object sender, EventArgs e)
{
resultLabel.Text = String.Empty;
this.numericUpDown1.Enabled = false;
this.startAsyncButton.Enabled = false;
this.cancelAsyncButton.Enabled = true;
//获取计算数值.
int numberToCompute = (int)numericUpDown1.Value;
//启动异步操作.
backgroundWorker1.RunWorkerAsync(numberToCompute);
}
|
|
void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
e.Result = ComputeAdd((int)e.Argument, worker, e);
}
|
|
private long ComputeAdd(int n, BackgroundWorker worker, DoWorkEventArgs e)
{
long result = 0;
for (int i = 1; i <= n; i++)
{
if (worker.CancellationPending)
{
e.Cancel = true;
break;
}
else
{
result += i;
Thread.Sleep(500);
int percentComplete = (int)((float)i / (float)n * 100);
worker.ReportProgress(percentComplete);
}
}
return result;
}
|
|
void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar1.Value = e.ProgressPercentage;
}
|
|
void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Error != null)
{
MessageBox.Show(e.Error.Message);
}
else if (e.Cancelled)
{
resultLabel.Text = "Canceled";
}
else
{
resultLabel.Text = e.Result.ToString();
}
this.numericUpDown1.Enabled = true;
startAsyncButton.Enabled = true;
cancelAsyncButton.Enabled = false;
}
|
|
public ProcessForm(BackgroundWorker backgroundWorker1)
{
InitializeComponent();
this.backgroundWorker1 = backgroundWorker1;
this.backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
this.backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
}
void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
this.Close();
}
void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
this.progressBar1.Value = e.ProgressPercentage;
}
private void cancelButton1_Click(object sender, EventArgs e)
{
this.backgroundWorker1.CancelAsync();
this.cancelButton1.Enabled = false;
this.Close();
}
|
|
private void startAsyncButton_Click(object sender, EventArgs e)
{
// ...
backgroundWorker1.RunWorkerAsync(numberToCompute);
ProcessForm form = new ProcessForm(this.backgroundWorker1);
form.ShowDialog(this);//模式
//form.Show(this);//非模式
}
|
|
publicvoidPost(SendOrPostCallback d,Object arg);
publicvoidPostOperationCompleted(SendOrPostCallback d,Object arg);
|
|
publicdelegatevoidSendOrPostCallback(Object state);
|
|
private delegate void WorkerThreadStartDelegate(object argument);
private readonly WorkerThreadStartDelegate threadStart;
public BackgroundWorker()
{
this.threadStart = new WorkerThreadStartDelegate(this.WorkerThreadStart);
//…
}
|
|
public void RunWorkerAsync(object argument)
{
if (this.isRunning)
{
throw new InvalidOperationException(SR.GetString("BackgroundWorker_WorkerAlreadyRunning"));
}
this.isRunning = true;
this.cancellationPending = false;
this.asyncOperation = AsyncOperationManager.CreateOperation(null);
this.threadStart.BeginInvoke(argument, null, null);
}
|
|
private void WorkerThreadStart(object argument)
{
object result = null;
Exception error = null;
bool cancelled = false;
try
{
DoWorkEventArgs e = new DoWorkEventArgs(argument);
this.OnDoWork(e);
if (e.Cancel)
{
cancelled = true;
}
else
{
result = e.Result;
}
}
catch (Exception exception2)
{
error = exception2;
}
RunWorkerCompletedEventArgs arg = new RunWorkerCompletedEventArgs(result, error, cancelled);
this.asyncOperation.PostOperationCompleted(this.operationCompleted, arg);
}
|
|
public void ReportProgress(int percentProgress, object userState)
{
if (!this.WorkerReportsProgress)
{
throw new InvalidOperationException(SR.GetString("BackgroundWorker_WorkerDoesntReportProgress"));
}
ProgressChangedEventArgs arg = new ProgressChangedEventArgs(percentProgress, userState);
if (this.asyncOperation != null)
{
this.asyncOperation.Post(this.progressReporter, arg);
}
else
{
this.progressReporter(arg);
}
}
|
|
public BackgroundWorker()
{
this.threadStart = new WorkerThreadStartDelegate(this.WorkerThreadStart);
this.operationCompleted = new SendOrPostCallback(this.AsyncOperationCompleted);
this.progressReporter = new SendOrPostCallback(this.ProgressReporter);
}
private void ProgressReporter(object arg)
{
this.OnProgressChanged((ProgressChangedEventArgs)arg);
}
private void AsyncOperationCompleted(object arg)
{
this.isRunning = false;
this.cancellationPending = false;
this.OnRunWorkerCompleted((RunWorkerCompletedEventArgs)arg);
}
|
|
public void RunWorkerAsync(object argument)
{
if (this.isRunning)
{
throw new InvalidOperationException(SR.GetString("BackgroundWorker_WorkerAlreadyRunning"));
}
this.isRunning = true;
this.cancellationPending = false;
this.asyncOperation = AsyncOperationManager.CreateOperation(null);
this.threadStart.BeginInvoke(argument, null, null);
}
public void CancelAsync()
{
if (!this.WorkerSupportsCancellation)
{
throw new InvalidOperationException(SR.GetString("BackgroundWorker_WorkerDoesntSupportCancellation"));
}
this.cancellationPending = true;
}
|
本文应用地址：http://blog.csdn.net/zhzuo/archive/2008/07/23/2699305.aspx
标签：
原文地址：http://www.cnblogs.com/mschen/p/4560065.html
