BackgroundWorker.RunWorkerCompleted BackgroundWorker.RunWorkerCompleted BackgroundWorker.RunWorkerCompleted BackgroundWorker.RunWorkerCompleted Event

Definición

Se produce cuando la operación en segundo plano se ha completado, se ha cancelado o ha producido una excepción.Occurs when the background operation has completed, has been canceled, or has raised an exception.

public:
 event System::ComponentModel::RunWorkerCompletedEventHandler ^ RunWorkerCompleted;
public event System.ComponentModel.RunWorkerCompletedEventHandler RunWorkerCompleted;
member this.RunWorkerCompleted : System.ComponentModel.RunWorkerCompletedEventHandler 
Public Custom Event RunWorkerCompleted As RunWorkerCompletedEventHandler 

Ejemplos

En el ejemplo de código siguiente se muestra el uso de la RunWorkerCompleted eventos para controlar el resultado de una operación asincrónica.The following code example demonstrates the use of the RunWorkerCompleted event to handle the result of an asynchronous operation. Este ejemplo de código forma parte de un ejemplo más extenso proporcionado para el BackgroundWorker clase.This code example is part of a larger example provided for the BackgroundWorker class.

// This event handler deals with the results of the
// background operation.
void backgroundWorker1_RunWorkerCompleted( Object^ /*sender*/, RunWorkerCompletedEventArgs^ e )
{
   // First, handle the case where an exception was thrown.
   if ( e->Error != nullptr )
   {
      MessageBox::Show( e->Error->Message );
   }
   else
   if ( e->Cancelled )
   {
      // Next, handle the case where the user cancelled 
      // the operation.
      // Note that due to a race condition in 
      // the DoWork event handler, the Cancelled
      // flag may not have been set, even though
      // CancelAsync was called.
      resultLabel->Text = "Cancelled";
   }
   else
   {
      // Finally, handle the case where the operation 
      // succeeded.
      resultLabel->Text = e->Result->ToString();
   }

   // Enable the UpDown control.
   this->numericUpDown1->Enabled = true;

   // Enable the Start button.
   startAsyncButton->Enabled = true;

   // Disable the Cancel button.
   cancelAsyncButton->Enabled = false;
}
// This event handler deals with the results of the
// background operation.
private void backgroundWorker1_RunWorkerCompleted(
    object sender, RunWorkerCompletedEventArgs e)
{
    // First, handle the case where an exception was thrown.
    if (e.Error != null)
    {
        MessageBox.Show(e.Error.Message);
    }
    else if (e.Cancelled)
    {
        // Next, handle the case where the user canceled 
        // the operation.
        // Note that due to a race condition in 
        // the DoWork event handler, the Cancelled
        // flag may not have been set, even though
        // CancelAsync was called.
        resultLabel.Text = "Canceled";
    }
    else
    {
        // Finally, handle the case where the operation 
        // succeeded.
        resultLabel.Text = e.Result.ToString();
    }

    // Enable the UpDown control.
    this.numericUpDown1.Enabled = true;

    // Enable the Start button.
    startAsyncButton.Enabled = true;

    // Disable the Cancel button.
    cancelAsyncButton.Enabled = false;
}
' This event handler deals with the results of the
' background operation.
Private Sub backgroundWorker1_RunWorkerCompleted( _
ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) _
Handles backgroundWorker1.RunWorkerCompleted

    ' First, handle the case where an exception was thrown.
    If (e.Error IsNot Nothing) Then
        MessageBox.Show(e.Error.Message)
    ElseIf e.Cancelled Then
        ' Next, handle the case where the user canceled the 
        ' operation.
        ' Note that due to a race condition in 
        ' the DoWork event handler, the Cancelled
        ' flag may not have been set, even though
        ' CancelAsync was called.
        resultLabel.Text = "Canceled"
    Else
        ' Finally, handle the case where the operation succeeded.
        resultLabel.Text = e.Result.ToString()
    End If

    ' Enable the UpDown control.
    Me.numericUpDown1.Enabled = True

    ' Enable the Start button.
    startAsyncButton.Enabled = True

    ' Disable the Cancel button.
    cancelAsyncButton.Enabled = False
End Sub 'backgroundWorker1_RunWorkerCompleted

Comentarios

Este evento se desencadena cuando el DoWork devuelve el controlador de eventos.This event is raised when the DoWork event handler returns.

Si la operación se completa correctamente y su resultado se asigna en el DoWork controlador de eventos, puede obtener acceso al resultado a través de la RunWorkerCompletedEventArgs.Result propiedad.If the operation completes successfully and its result is assigned in the DoWork event handler, you can access the result through the RunWorkerCompletedEventArgs.Result property.

El Error propiedad de System.ComponentModel.RunWorkerCompletedEventArgs indica que se produjo una excepción por la operación.The Error property of System.ComponentModel.RunWorkerCompletedEventArgs indicates that an exception was thrown by the operation.

El Cancelled propiedad de System.ComponentModel.RunWorkerCompletedEventArgs indica si la operación en segundo plano ha procesado una solicitud de cancelación.The Cancelled property of System.ComponentModel.RunWorkerCompletedEventArgs indicates whether a cancellation request was processed by the background operation. Si su código en el DoWork controlador de eventos detecta una solicitud de cancelación mediante la comprobación de la CancellationPending marca y estableciendo el Cancel marca de System.ComponentModel.DoWorkEventArgs a true, el Cancelled marca de System.ComponentModel.RunWorkerCompletedEventArgs también se establecerá en true.If your code in the DoWork event handler detects a cancellation request by checking the CancellationPending flag and setting the Cancel flag of System.ComponentModel.DoWorkEventArgs to true, the Cancelled flag of System.ComponentModel.RunWorkerCompletedEventArgs also will be set to true.

Precaución

Tenga en cuenta que el código en el DoWork controlador de eventos puede finalizar su trabajo mientras se realiza una solicitud de cancelación y el bucle de sondeo puede perder CancellationPending se establece en true.Be aware that your code in the DoWork event handler may finish its work as a cancellation request is being made, and your polling loop may miss CancellationPending being set to true. En este caso, el Cancelled marca de System.ComponentModel.RunWorkerCompletedEventArgs en su RunWorkerCompleted controlador de eventos no se establecerá en true, aunque se realizó una solicitud de cancelación.In this case, the Cancelled flag of System.ComponentModel.RunWorkerCompletedEventArgs in your RunWorkerCompleted event handler will not be set to true, even though a cancellation request was made. Esta situación se denomina un condición de carrera y es un problema habitual en la programación multiproceso.This situation is called a race condition and is a common concern in multithreaded programming. Para obtener más información sobre el diseño multithreading problemas, vea Managed Threading Best Practices.For more information about multithreading design issues, see Managed Threading Best Practices.

Su RunWorkerCompleted controlador de eventos debe comprobar siempre el AsyncCompletedEventArgs.Error y AsyncCompletedEventArgs.Cancelled propiedades antes de acceder a la RunWorkerCompletedEventArgs.Result propiedad.Your RunWorkerCompleted event handler should always check the AsyncCompletedEventArgs.Error and AsyncCompletedEventArgs.Cancelled properties before accessing the RunWorkerCompletedEventArgs.Result property. Si se generó una excepción o si se ha cancelado la operación, obtener acceso a la RunWorkerCompletedEventArgs.Result propiedad produce una excepción.If an exception was raised or if the operation was canceled, accessing the RunWorkerCompletedEventArgs.Result property raises an exception.

Se aplica a

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