BackgroundWorker.RunWorkerAsync Method

Definition

Namespace:

System.ComponentModel

Assembly:

System.ComponentModel.EventBasedAsync.dll

Starts execution of a background operation.

Overloads

RunWorkerAsync()	Starts execution of a background operation.
RunWorkerAsync(Object)	Starts execution of a background operation.

RunWorkerAsync()

Source:

BackgroundWorker.cs

Starts execution of a background operation.

public:
 void RunWorkerAsync();

public void RunWorkerAsync ();

member this.RunWorkerAsync : unit -> unit

Public Sub RunWorkerAsync ()

Exceptions

InvalidOperationException

IsBusy is true.

Examples

The following code example demonstrates the use of the RunWorkerAsync method to start an asynchronous operation. It is part of a larger example described in How to: Download a File in the Background.

private void downloadButton_Click(object sender, EventArgs e)
{
    // Start the download operation in the background.
    this.backgroundWorker1.RunWorkerAsync();

    // Disable the button for the duration of the download.
    this.downloadButton.Enabled = false;

    // Once you have started the background thread you 
    // can exit the handler and the application will 
    // wait until the RunWorkerCompleted event is raised.

    // Or if you want to do something else in the main thread,
    // such as update a progress bar, you can do so in a loop 
    // while checking IsBusy to see if the background task is
    // still running.

    while (this.backgroundWorker1.IsBusy)
    {
        progressBar1.Increment(1);
        // Keep UI messages moving, so the form remains 
        // responsive during the asynchronous operation.
        Application.DoEvents();
    }
}

Private Sub downloadButton_Click( _
    ByVal sender As Object, _
    ByVal e As EventArgs) _
    Handles downloadButton.Click

    ' Start the download operation in the background.
    Me.backgroundWorker1.RunWorkerAsync()

    ' Disable the button for the duration of the download.
    Me.downloadButton.Enabled = False

    ' Once you have started the background thread you 
    ' can exit the handler and the application will 
    ' wait until the RunWorkerCompleted event is raised.

    ' If you want to do something else in the main thread,
    ' such as update a progress bar, you can do so in a loop 
    ' while checking IsBusy to see if the background task is
    ' still running.
    While Me.backgroundWorker1.IsBusy
        progressBar1.Increment(1)
        ' Keep UI messages moving, so the form remains 
        ' responsive during the asynchronous operation.
        Application.DoEvents()
    End While
End Sub

Remarks

The RunWorkerAsync method submits a request to start the operation running asynchronously. When the request is serviced, the DoWork event is raised, which in turn starts execution of your background operation.

If the background operation is already running, calling RunWorkerAsync again will raise an InvalidOperationException.

See also

• DoWork
• How to: Run an Operation in the Background
• Managed Threading Best Practices
• How to: Download a File in the Background

RunWorkerAsync(Object)

Source:

BackgroundWorker.cs

Starts execution of a background operation.

public:
 void RunWorkerAsync(System::Object ^ argument);

public void RunWorkerAsync (object? argument);

member this.RunWorkerAsync : obj -> unit

Public Sub RunWorkerAsync (argument As Object)

Parameters

argument

Object

A parameter for use by the background operation to be executed in the DoWork event handler.

Exceptions

InvalidOperationException

IsBusy is true.

Examples

The following code example demonstrates the use of the RunWorkerAsync method to start an asynchronous operation. This code example is part of a larger example provided for the BackgroundWorker class.

// Start the asynchronous operation.
backgroundWorker1->RunWorkerAsync( numberToCompute );

// Start the asynchronous operation.
backgroundWorker1.RunWorkerAsync(numberToCompute);

' Start the asynchronous operation.
backgroundWorker1.RunWorkerAsync(numberToCompute)

Remarks

The RunWorkerAsync method submits a request to start the operation running asynchronously. When the request is serviced, the DoWork event is raised, which in turn starts execution of your background operation.

If your operation requires a parameter, you can provide it as the argument parameter to RunWorkerAsync.

If the background operation is already running, calling RunWorkerAsync again will raise an InvalidOperationException.

See also

• DoWork
• How to: Run an Operation in the Background
• How to: Download a File in the Background
• Managed Threading Best Practices