我有一个后台工作者,它从数据库中收集大量数据。我想在线程上设置一个超时限制,以便如果它在设定的时间后没有返回结果,则取消该过程。
我在启动 BackgroundWorker 的同时在主线程上启动了一个计时器。
如果我故意让 BGW 进入睡眠状态,计时器就会过去并调用 .Elapsed 事件。然后它取消后台工作人员,但是它没有成功完成我希望它完成的其他操作,即更新 GUI 上的状态栏并抛出 MessageBox。我不明白为什么不,有人可以帮忙吗?
超时和睡眠是专门为测试设置的。
/// <summary>
/// loads Assets by group ID
/// Populates Grid on asset listing page
/// </summary>
/// <param name="groupId"></param>
/// <param name="user"></param>
internal void PopulateGridAssetsByGroup(int groupId, User user)
{
//update statusbar
AfMainWindow.MainWindow.UpdateStatusBar("Loading Assets...");
//setup BG worker
populateGridAssetsWorker = new BackgroundWorker {WorkerSupportsCancellation = true, WorkerReportsProgress = false};
populateGridAssetsWorker.DoWork += populateGridAssetsWorker_DoWork;
populateGridAssetsWorker.RunWorkerCompleted += populateGridAssetsWorker_RunWorkerCompleted;
//setup timer which will cancel the background worker if it runs too long
cancelTimer = new Timer {Interval = 2000, Enabled = true, AutoReset = false};
cancelTimer.Elapsed += cancelTimer_Elapsed;
cancelTimer.Start();
populateGridAssetsWorker.RunWorkerAsync(groupId); //start bg worker
}
void cancelTimer_Elapsed(object sender, ElapsedEventArgs e)
{
populateGridAssetsWorker.CancelAsync();
cancelTimer.Stop();
AfMainWindow.MainWindow.UpdateStatusBar("Could not load assets, timeout error");
MessageBox.Show("Operation Timed Out\n\nThe Server did not respond quick enough, please try again",
"Timeout", MessageBoxButton.OK, MessageBoxImage.Exclamation, MessageBoxResult.OK);
AfMainWindow.MainWindow.Busy.IsBusy = false;
}
/// <summary>
/// when bg worker complete, update the AssetGrid on Asset Listing Page with results
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void populateGridAssetsWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
cancelTimer.Stop();
//my thread complete processing
}
/// <summary>
/// Perform the DB query and collect results for asset listing
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
void populateGridAssetsWorker_DoWork(object sender, DoWorkEventArgs e)
{
var assetListByGroup = new List<AssetLinked>();
Thread.Sleep(5000);
if (populateGridAssetsWorker.CancellationPending)
{
return;
}
try
{
//My SQL actions
if (populateGridAssetsWorker.CancellationPending)
{
return;
}
}
catch (Exception ex)
{
Globals.AFWideSettings.GeneralErrorMessage(ex.Message);
}
}