Order of Window Opening and Closing

I have two windows:  MainWindow and Window2

1) On the initial opening of the application I would like Window2 to open.

2) When I click the button on Window2 it will close this window and MainWindow will open. (If I close Window2 instead of clicking the button, then I want the app to shut down)

3) MainWindow will now be the only window open.

4) When I click the button on MainWindow it will open Window2 as a DIALOG window.

5) When Window2 is open as a dialog, I want to be able to close the dialog and STILL HAVE MainWindow OPEN. (***currently, the app shuts down when I close the dialog window)

How can I accomplish these goals?

The main problems with the below app is that:  Window2 doesn't open FIRST and closing the dialog window WHILE MainWindow is open shuts down the app.

MainWindow XAML:

<Window x:Class="WpfApplication41.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"><Grid><Button Content="Open Window2" Height="29" HorizontalAlignment="Left" 
                Margin="184,51,0,0" Name="button1" VerticalAlignment="Top" Width="125" Click="button1_Click" /></Grid></Window>

MainWindow C#:

namespace WpfApplication41
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            Window2 win2 = new Window2();
            win2.WindowStartupLocation = WindowStartupLocation.Manual;

            win2.ShowDialog();
            this.Close();
        }
    }
}

Window2 XAML:

<Window x:Class="WpfApplication41.Window2"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="300" Width="335"><Grid><Button Content="Close this window" Height="27" HorizontalAlignment="Left" 
                Margin="78,42,0,0" Name="button1" VerticalAlignment="Top" Width="141" Click="button1_Click" /></Grid></Window>

namespace WpfApplication41
{
    public partial class Window2 : Window
    {
        public Window2()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, RoutedEventArgs e)
        {
            MainWindow win1 = new MainWindow();
            win1.WindowStartupLocation = WindowStartupLocation.Manual;

            win1.Show();
            this.Close();

        }


    }
}