BackgroundWorker.CancellationPending Eigenschaft
Definition
Wichtig
Einige Informationen beziehen sich auf Vorabversionen, die vor dem Release ggf. grundlegend überarbeitet werden. Microsoft übernimmt hinsichtlich der hier bereitgestellten Informationen keine Gewährleistungen, seien sie ausdrücklich oder konkludent.
Ruft einen Wert ab, der angibt, ob die Anwendung den Abbruch eines Hintergrundvorgangs angefordert hat.
public:
property bool CancellationPending { bool get(); };public bool CancellationPending { get; }[System.ComponentModel.Browsable(false)]
public bool CancellationPending { get; }member this.CancellationPending : bool[<System.ComponentModel.Browsable(false)>]
member this.CancellationPending : boolPublic ReadOnly Property CancellationPending As BooleanEigenschaftswert
truewenn die Anwendung den Abbruch eines Hintergrundvorgangs angefordert hat; andernfalls . false Der Standardwert lautet false.
- Attribute
Beispiele
Das folgende Codebeispiel veranschaulicht die Verwendung der CancellationPending Eigenschaft zum Abfragen eines BackgroundWorker Abbruchzustands. Dieses Codebeispiel ist Teil eines größeren Beispiels, das für die BackgroundWorker Klasse bereitgestellt wird.
// Abort the operation if the user has cancelled.
// Note that a call to CancelAsync may have set
// CancellationPending to true just after the
// last invocation of this method exits, so this
// code will not have the opportunity to set the
// DoWorkEventArgs.Cancel flag to true. This means
// that RunWorkerCompletedEventArgs.Cancelled will
// not be set to true in your RunWorkerCompleted
// event handler. This is a race condition.
if ( worker->CancellationPending )
{
e->Cancel = true;
}
else
{
if ( n < 2 )
{
result = 1;
}
else
{
result = ComputeFibonacci( n - 1, worker, e ) + ComputeFibonacci( n - 2, worker, e );
}
// Report progress as a percentage of the total task.
int percentComplete = (int)((float)n / (float)numberToCompute * 100);
if ( percentComplete > highestPercentageReached )
{
highestPercentageReached = percentComplete;
worker->ReportProgress( percentComplete );
}
}
// Abort the operation if the user has canceled.
// Note that a call to CancelAsync may have set
// CancellationPending to true just after the
// last invocation of this method exits, so this
// code will not have the opportunity to set the
// DoWorkEventArgs.Cancel flag to true. This means
// that RunWorkerCompletedEventArgs.Cancelled will
// not be set to true in your RunWorkerCompleted
// event handler. This is a race condition.
if (worker.CancellationPending)
{
e.Cancel = true;
}
else
{
result = n < 2
? 1
: ComputeFibonacci(n - 1, worker, e) +
ComputeFibonacci(n - 2, worker, e);
// Report progress as a percentage of the total task.
int percentComplete =
(int)(n / (float)numberToCompute * 100);
if (percentComplete > highestPercentageReached)
{
highestPercentageReached = percentComplete;
worker.ReportProgress(percentComplete);
}
}
' Abort the operation if the user has canceled.
' Note that a call to CancelAsync may have set
' CancellationPending to true just after the
' last invocation of this method exits, so this
' code will not have the opportunity to set the
' DoWorkEventArgs.Cancel flag to true. This means
' that RunWorkerCompletedEventArgs.Cancelled will
' not be set to true in your RunWorkerCompleted
' event handler. This is a race condition.
If worker.CancellationPending Then
e.Cancel = True
Else
If n < 2 Then
result = 1
Else
result = ComputeFibonacci(n - 1, worker, e) +
ComputeFibonacci(n - 2, worker, e)
End If
' Report progress as a percentage of the total task.
Dim percentComplete As Integer =
CSng(n) / CSng(numberToCompute) * 100
If percentComplete > highestPercentageReached Then
highestPercentageReached = percentComplete
worker.ReportProgress(percentComplete)
End If
End If
Hinweise
Wenn CancellationPending dies der Wert ist true, wurde die CancelAsync Methode für die BackgroundWorker.
Diese Eigenschaft ist für die Verwendung durch den Workerthread vorgesehen, der den Hintergrundvorgang regelmäßig überprüfen CancellationPending und abbrechen sollte, wenn er auf festgelegt trueist.
