RunWorkerCompletedEventHandler Delegato

Definizione

Spazio dei nomi:

System.ComponentModel

Assembly:

System.dll

Rappresenta il metodo che gestirà l'evento RunWorkerCompleted di una BackgroundWorker classe.

public delegate void RunWorkerCompletedEventHandler(System::Object ^ sender, RunWorkerCompletedEventArgs ^ e);

public delegate void RunWorkerCompletedEventHandler(object sender, RunWorkerCompletedEventArgs e);

type RunWorkerCompletedEventHandler = delegate of obj * RunWorkerCompletedEventArgs -> unit

Public Delegate Sub RunWorkerCompletedEventHandler(sender As Object, e As RunWorkerCompletedEventArgs)

Parametri

sender

Object

La fonte dell'evento.

e

RunWorkerCompletedEventArgs

Oggetto RunWorkerCompletedEventArgs contenente i dati dell'evento.

Esempio

Nell'esempio di codice seguente viene illustrato un metodo che può essere usato come gestore per RunWorkerCompletedEventHandler. Questo esempio fa parte di un esempio più ampio per la BackgroundWorker classe .

// 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.
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.
    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.
    numericUpDown1.Enabled = True

    ' Enable the Start button.
    startAsyncButton.Enabled = True

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

Commenti

Quando si crea un RunWorkerCompletedEventHandler delegato, si identifica un metodo per gestire l'evento. Per associare l'evento al gestore eventi, aggiungere un'istanza del delegato all'evento. Il gestore eventi viene chiamato ogni volta che si verifica l'evento, a meno che non si rimuovono il delegato. Per altre informazioni sui delegati del gestore eventi, vedere Gestione e generazione di eventi.

Metodi di estensione

Nome	Descrizione
GetMethodInfo(Delegate)	Ottiene un oggetto che rappresenta il metodo rappresentato dal delegato specificato.