BackgroundWorker.CancellationPending Özellik

Tanım

Ad Alanı:

System.ComponentModel

Bütünleştirilmiş Kod:

System.ComponentModel.EventBasedAsync.dll

Kaynak:

BackgroundWorker.cs

Uygulamanın bir arka plan işleminin iptalini isteyip istemediğinizi belirten bir değer alır.

public:
 property bool CancellationPending { bool get(); };

public bool CancellationPending { get; }

member this.CancellationPending : bool

Public ReadOnly Property CancellationPending As Boolean

Özellik Değeri

Boolean

true uygulama bir arka plan işleminin iptalini istediyse; aksi takdirde , false. Varsayılan değer: false.

Örnekler

Aşağıdaki kod örneği, iptal durumunu sorgulamak BackgroundWorker için özelliğinin CancellationPending kullanımını gösterir. Bu kod örneği, sınıfı için BackgroundWorker sağlanan daha büyük bir örneğin parçasıdır.

// 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

Açıklamalar

ise CancellationPendingtrueyöntemi CancelAsync üzerinde BackgroundWorkerçağrılır.

Bu özellik, olarak ayarlandığında arka plan işlemini düzenli aralıklarla denetlemesi CancellationPending ve durdurması gereken çalışan iş parçacığı tarafından kullanılmak üzere truehazırlanmıştır.

Ayrıca bkz.

• Nasıl yapılır: Arka Planda İşlem Çalıştırma
• Nasıl yapılır: Arka Planda Dosya İndirme