Bagikan melalui

BackgroundWorker.CancellationPending Properti

  • Referensi

Definisi

Ruang nama:
System.ComponentModel
Rakitan:
System.dll, System.ComponentModel.EventBasedAsync.dll
Rakitan:
System.ComponentModel.EventBasedAsync.dll
Rakitan:
System.dll
Rakitan:
netstandard.dll
Sumber:
BackgroundWorker.cs
Sumber:
BackgroundWorker.cs
Sumber:
BackgroundWorker.cs

Mendapatkan nilai yang menunjukkan apakah aplikasi telah meminta pembatalan operasi latar belakang.

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

Nilai Properti

Boolean

true jika aplikasi telah meminta pembatalan operasi latar belakang; jika tidak, false. Default adalah false.

Atribut
BrowsableAttribute

Contoh

Contoh kode berikut menunjukkan penggunaan properti untuk mengkueri CancellationPendingBackgroundWorker tentang status pembatalannya. Contoh kode ini adalah bagian dari contoh yang lebih besar yang disediakan untuk BackgroundWorker kelas .

// 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

Keterangan

Jika CancellationPending adalah true, maka CancelAsync metode telah dipanggil pada BackgroundWorker.

Properti ini dimaksudkan untuk digunakan oleh utas pekerja, yang harus secara berkala memeriksa CancellationPending dan membatalkan operasi latar belakang ketika diatur ke true.

Berlaku untuk

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