C# – parallel process in wpf

Here is my scenario:
I have a Main ParentWindow .
Before opening the parent i would like to open a progressWindow and fetch the data from DB displaying this window.
After the data fetch is complete i would like to close the progressWindow by using a delegate and i am running into threading issues.
Just wondering if you have any suggestions:

Here is the code for ParentWindow:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Shapes;

namespace RounderProgressBar
{

/// <summary>
/// Interaction logic for Window2.xaml
/// </summary>

public partial class ParentWindow : Window
{

    public ParentWindow()
    {
        InitializeComponent();

        progress = new ProgressWindow();
        progress.publisher = this.Subscriber;
        progress.ShowDialog();
    }
    ProgressWindow progress;// = new Window1();
    protected EventHandlerWithParms _subscriber;
    protected EventHandlerWithParms Subscriber
    {
        get
        {
            if (_subscriber == null)
            {
                _subscriber = new EventHandlerWithParms(Execute);
            }
            return _subscriber;
        }
    }
    private void Execute(object sender, EventArgs e)
     {
        (sender as Window).Close();//.Dispatcher.Invoke(Subscriber,null);//.InvokeShutdown();//.Close();

        //progress.Close();
        //this.Close();
        //Window w = new Window();
        //w.ShowDialog();
    }
}

}

Here is the child or progressWindow:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows;

using System.Windows.Controls;

using System.Windows.Data;

using System.Windows.Documents;

using System.Windows.Input;

using System.Windows.Media;

using System.Windows.Media.Imaging;

using System.Windows.Navigation;

using System.Windows.Shapes;

using System.ComponentModel;

using System.Collections;

namespace RounderProgressBar
{

/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>

public partial class ProgressWindow : Window

{

    public ProgressWindow()

    {

        InitializeComponent();

        StartWorker(null, null);
    }

    private BackgroundWorker _worker;

    private void StartWorker(object sender, RoutedEventArgs e)
    {
        _worker = new BackgroundWorker();
        _worker.WorkerReportsProgress = true;
        _worker.WorkerSupportsCancellation = true;

        _worker.DoWork += delegate(object s, DoWorkEventArgs args)
        {
            BackgroundWorker worker = s as BackgroundWorker;
            //for (int i = 0; i < 10; i++)
            //{
            if (worker.CancellationPending)
            {
                args.Cancel = true;
                return;
            }

            //System.Threading.Thread.Sleep(1000);
            runInBack();
            //int max = int.Parse((_progressBar.Maximum - 1).ToString());

            //If we comment this it will go into infinite loop as completed will never get triggered
            //worker.ReportProgress(/*max*/9);//worker.ReportProgress(9);//worker.ReportProgress(i + 1);
            worker.ReportProgress(9);
            //}
        };

        _worker.ProgressChanged += delegate(object s, ProgressChangedEventArgs args)
        {
            //_progressBar.Value = args.ProgressPercentage;
        };

        _worker.RunWorkerCompleted += delegate(object s, RunWorkerCompletedEventArgs args)
        {
            //_btnStart.IsEnabled = true;
            //_btnCancel.IsEnabled = false;
            //_progressBar.Value = 0;
        };

        _worker.RunWorkerAsync();
        //_btnStart.IsEnabled = false;
        //_btnCancel.IsEnabled = true;
    }
    private void runInBack()
    {
        System.Threading.Thread.Sleep(3000);
        //IsBusExecuted = true;
        if (this.publisher != null)
            publisher(this, null);
    }
    public EventHandlerWithParms publisher;
    private void CancelWorker(object sender, RoutedEventArgs e)
    {
        _worker.CancelAsync();
    }

    private bool IsBusExecuted = false;
    void t_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {
        if (IsBusExecuted)
        {
            t.Stop();
            MessageBox.Show("1");
            this.rpb.Stop();
        }

    }

    private void Execute(object sender, EventArgs e)
    {
        this.Close();
    }

    private System.Timers.Timer t = new System.Timers.Timer(1000);
}
public delegate void EventHandlerWithParms(object sender, EventArgsWithParms e);
public class EventArgsWithParms : EventArgs
{
    public EventArgsWithParms()
    {
    }
    public Hashtable ParmTable = new Hashtable();
}

}