How can I wait for BackgroundWorker to complete?

Question

I would like to use BackgroundWorkera database from a GUI to execute a transaction.

How can I command BackgroundWorkerto execute work, and then WAIT for execution by an employee, while maintaining a graphical interface?

Should I use DoEventsfor this purpose or is there another way?

Answer 1

By asking, "How can I command BackgroundWorkerto complete this work, and then WAIT so that the employee can complete, while maintaining the graphical interface?" really asks: "How to use BackgroundWorker?". What does BackgroundWorker.

When you write a background task, you basically break the method into four parts:

• Preparation for the task.
• The task itself.
• Report on progress in the user interface during task execution.
• Cleaning an object when performing a task.

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Answer 2

RunWorkerCompleted . , , ..

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Answer 3

:

Application.DoEvents();

backgroundworker

, :

// The declaration of the textbox.
private TextBox m_TextBox;

// Updates the textbox text.
private void UpdateText(string text)
{
    // Set the textbox text.
    m_TextBox.Text = text;
}


public delegate void UpdateTextCallback(string text);

Invoke m_TextBox, , .

m_TextBox.Invoke(new UpdateTextCallback(this.UpdateText),
                 new object[]{"Text generated on non-UI thread."});

,

Answer 4

You can call RunWorkerAsync as follows:

this.backgroundWorker1.RunWorkerAsync();

And then you will need to use the RunWorkerCompleted event .

Here is an example from MSDN:

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;
}

What is it. I do not think there is a need to call DoEvents. The user interface should still respond while BackgroundWorker is running.