BackgroundWorker.CancellationPending Propriété

Référence

Définition

Espace de noms:: System.ComponentModel

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

Assembly:: System.ComponentModel.EventBasedAsync.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Source:: BackgroundWorker.cs

Source:: BackgroundWorker.cs

Source:: BackgroundWorker.cs

Important

Certaines informations portent sur la préversion du produit qui est susceptible d’être en grande partie modifiée avant sa publication. Microsoft exclut toute garantie, expresse ou implicite, concernant les informations fournies ici.

Obtient une valeur qui indique si l'application a demandé l'annulation d'une opération d'arrière-plan.

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

Valeur de propriété

Boolean

true si l'application a demandé l'annulation d'une opération d'arrière-plan ; sinon, false. La valeur par défaut est false.

Attributs: BrowsableAttribute

Exemples

L’exemple de code suivant illustre l’utilisation de la CancellationPending propriété pour interroger un BackgroundWorker sur son état d’annulation. Cet exemple de code fait partie d’un exemple plus grand fourni pour la BackgroundWorker classe .

// 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

Remarques

Si CancellationPending a la valeur true, la CancelAsync méthode a été appelée sur .BackgroundWorker

Cette propriété est destinée à être utilisée par le thread de travail, qui doit régulièrement case activée CancellationPending et abandonner l’opération d’arrière-plan lorsqu’elle est définie sur true.

S’applique à

Partager via