Condividi tramite

RunWorkerCompletedEventArgs.Result Proprietà

  • Riferimento

Definizione

Spazio dei nomi:
System.ComponentModel
Assembly:
System.dll, System.ComponentModel.EventBasedAsync.dll
Assembly:
System.ComponentModel.EventBasedAsync.dll
Assembly:
System.dll
Assembly:
netstandard.dll
Source:
RunWorkerCompletedEvent.cs
Source:
RunWorkerCompletedEvent.cs
Source:
RunWorkerCompletedEvent.cs

Ottiene un valore che rappresenta il risultato di un'operazione asincrona.

public:
 property System::Object ^ Result { System::Object ^ get(); };
public object Result { get; }
public object? Result { get; }
member this.Result : obj
Public ReadOnly Property Result As Object

Valore della proprietà

Object

Oggetto Object che rappresenta il risultato di un'operazione asincrona.

Eccezioni

TargetInvocationException

Error non è null. La proprietà InnerException contiene un riferimento a Error.

InvalidOperationException

Cancelled è true.

Esempio

Nell'esempio di codice seguente viene illustrato l'uso dell'evento RunWorkerCompleted per gestire il risultato di un'operazione asincrona. Questo esempio di codice fa parte di un esempio più ampio fornito 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.
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

Commenti

Il RunWorkerCompleted gestore eventi deve sempre controllare le Error proprietà e Cancelled prima di accedere alla Result proprietà . Se è stata generata un'eccezione o se l'operazione è stata annullata, l'accesso alla Result proprietà genera un'eccezione.

Si applica a

Vedi anche