BackgroundWorker.CancellationPending Eigenschaft

Referenz

Definition

Namespace:: System.ComponentModel

Assemblys:: System.dll, System.ComponentModel.EventBasedAsync.dll

Assembly:: System.ComponentModel.EventBasedAsync.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Quelle:: BackgroundWorker.cs

Quelle:: BackgroundWorker.cs

Quelle:: BackgroundWorker.cs

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 : bool

Public ReadOnly Property CancellationPending As Boolean

Eigenschaftswert

Boolean

true, wenn die Anwendung den Abbruch eines Hintergrundvorgangs angefordert hat, andernfalls false. Der Standardwert ist false.

Attribute: BrowsableAttribute

Beispiele

Im folgenden Codebeispiel wird die Verwendung der CancellationPending -Eigenschaft zum Abfragen des Abbruchstatus veranschaulicht BackgroundWorker . 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
{   
    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 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 ist true, wurde die CancelAsync -Methode für aufgerufen BackgroundWorker.

Diese Eigenschaft ist für die Verwendung durch den Workerthread vorgesehen, der den Hintergrundvorgang regelmäßig überprüfen CancellationPending und abbrechen sollte, wenn er auf truefestgelegt ist.

Gilt für:

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