BackgroundWorker.CancellationPending Property (System.ComponentModel)

CancellationPending Property

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

BackgroundWorker..::.CancellationPending Property

Updated: November 2007

Gets a value indicating whether the application has requested cancellation of a background operation.

Namespace: System.ComponentModel
Assembly: System (in System.dll)

Syntax

Visual Basic (Declaration)

<BrowsableAttribute(False)> _
Public ReadOnly Property CancellationPending As Boolean

Visual Basic (Usage)

Dim instance As BackgroundWorker
Dim value As Boolean

value = instance.CancellationPending

[BrowsableAttribute(false)]
public bool CancellationPending { get; }

Visual C++

[BrowsableAttribute(false)]
public:
property bool CancellationPending {
    bool get ();
}

/** @property */
/** @attribute BrowsableAttribute(false) */
public boolean get_CancellationPending()

JScript

public function get CancellationPending () : boolean

Property Value

Type: System..::.Boolean

true if the application has requested cancellation of a background operation; otherwise, false. The default is false.

Remarks

If CancellationPending is true, then the CancelAsync method has been called on the BackgroundWorker.

This property is meant for use by the worker thread, which should periodically check CancellationPending and abort the background operation when it is set to true.

Examples

The following code example demonstrates the use of the CancellationPending property to query a BackgroundWorker about its cancellation state. This code example is part of a larger example provided for the BackgroundWorker class.

Visual Basic

' 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

// 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);
    }
}

Visual C++

// 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 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.get_CancellationPending()) {

    e.set_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);
    }
}

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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