Wpf Backgroundworker

<Window x:Class="WpfApp53.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp53"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <ListBox Grid.Row="0" x:Name="listBox1"/>
        <ProgressBar Grid.Row="1" x:Name="progressBar1" Height="20" Margin="5"/>
        <StackPanel Grid.Row="2" Orientation="Horizontal" Margin="5">
            <TextBlock Text="Status: "/>
            <TextBlock x:Name="statusTextBox"/>
        </StackPanel>
        <Grid Grid.Row="3" Margin="10">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Button Grid.Column="0" x:Name="startBtn" Content="Start" Click="StartBtn_Click"/>
            <Button Grid.Column="1" x:Name="cancelBtn" Content="Cancel" Click="CancelBtn_Click"/>
        </Grid>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
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;

namespace WpfApp53
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        BackgroundWorker bgWorker;
        public MainWindow()
        {
            InitializeComponent();
            cancelBtn.IsEnabled = false;
        }

        private void StartBtn_Click(object sender, RoutedEventArgs e)
        {
            listBox1.Items.Clear();
            startBtn.IsEnabled = false;
            cancelBtn.IsEnabled = true;
            bgWorker = new BackgroundWorker();
            bgWorker.DoWork += BgWorker_DoWork;
            bgWorker.ProgressChanged += BgWorker_ProgressChanged;
            bgWorker.RunWorkerCompleted += BgWorker_RunWorkerCompleted;
            bgWorker.WorkerReportsProgress = true;
            bgWorker.WorkerSupportsCancellation = true;

            int maxItems = 50;
            progressBar1.Minimum = 1;
            progressBar1.Maximum = 100;

            statusTextBox.Text = "Starting...";
            bgWorker.RunWorkerAsync(maxItems);
        }

        private void BgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
             if(e.Cancelled)
            {
                statusTextBox.Text = "Cancelled";
            }
            else
            {
                statusTextBox.Text = "Completed";
            }
            statusTextBox.IsEnabled = true;
            cancelBtn.IsEnabled = false;
        }

        private void BgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            double percent = (e.ProgressPercentage * 100) / 50;
            progressBar1.Value = Math.Round(percent, 0);
            listBox1.Items.Add(new ListBoxItem { Content = e.ProgressPercentage + " item added" });
            statusTextBox.Text = Math.Round(percent, 0) + "% percent completed";
        }

        private void BgWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            int? maxItems = e.Argument as int?;
            for(int i=1;i<=maxItems.GetValueOrDefault();i++)
            {
                if(bgWorker.CancellationPending)
                {
                    e.Cancel = true;
                    break;
                }
                Thread.Sleep(200);
                bgWorker.ReportProgress(i);
            }
        }

        private void CancelBtn_Click(object sender, RoutedEventArgs e)
        {
            bgWorker.CancelAsync();
            startBtn.IsEnabled = true;
        }
    }
}