RunWorkerCompletedEventArgs.Result Property
Definition
Important
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Gets a value that represents the result of an asynchronous operation.
public:
property System::Object ^ Result { System::Object ^ get(); };public object Result { get; }public object? Result { get; }member this.Result : objPublic ReadOnly Property Result As ObjectProperty Value
An Object representing the result of an asynchronous operation.
Exceptions
Error is not null. The InnerException property holds a reference to Error.
Cancelled is true.
Examples
The following code example demonstrates the use of the RunWorkerCompleted event to handle the result of an asynchronous operation. 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
Remarks
Your RunWorkerCompleted event handler should always check the Error and Cancelled properties before accessing the Result property. If an exception was raised or if the operation was canceled, accessing the Result property raises an exception.
