/// <summary>

/// This flag is used to restart the BackroundWorker process

/// </summary>

private bool _restartSearchBackroundWorker;

/// <summary>

/// This starts the Backroundworker process

/// </summary>

void StartSearch() {

    // check if the worker is already running

    if (searchBackgroundWorker.IsBusy) {

        // we want the BackgroundWorker to restart when it's finnished

        _restartSearchBackroundWorker = true;

        // Cancel current background operations

        searchBackroundWorker.CancelAsync();

    } else {

        // Start the operation - here we start retrieving Data of a SQL database with Searchtext

        searchBackroundWorker.RunWorkerAsync(textBoxSearchInput.Text);

    }

}

/// <summary>

/// This cancels the Backgroundworker

/// Can be used either by the Application, or in the Form closed event

/// </summary>

private void CancelSearch() {

    if (searchBackgroundWorker.IsBusy) {

        // No - we won't restart the BackgroundWorker

        _restartSearchBackroundWorker = false;

        // Cancel current background operations

        searchBackgroundWorker.CancelAsync();

    }

}

/// <summary>

/// The BackgroundWorker DoWork Method

/// </summary>

private void searchBackgroundWorker_DoWork(object sender, DoWorkEventArgs e) {

    BackgroundWorker w = (BackgroundWorker)sender;

    // this is a class that generates a SQL request for our application

    SearchFilter filter = new SearchFilter(e.Argument.ToString());

    // usually here you would do a long running process, that would block the user interface

    // in a for-each loop you have to check the 

    // w.CancellationPending parameter and exit the loop when it's set

    DataService dataService = new DataService(Globals.Settings.SqlConnectionString);

    e.Result = dataService.ExecuteQuery(filter);

}

/// <summary>

/// This is the RunWorkerCompleted event.

/// Itis called when the BackgroundWorker has finnished the operation

/// </summary>

private void searchBackgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {

    // When the operation has been canceled

    if (e.Cancelled) {

        // check if the BackgroundWorker has to be re-started

        if (_restartSearchBackroundWorker) {

            // If you want to re-start, clear the flag

            _restartSearchBackroundWorker = false;

            // re-start the BackgroundWorker

            downLoader.RunWorkerAsync(textBoxSearchInput.Text);

        }

    } else {

        // When the operation has not been canceled, use the result 

        IEnumerable<IClientRow> result = (IEnumerable<IClientRow>)e.Result;

        // TODO: Do something with the result

    }

}