Open BaseMetroDialog in another BaseMetroDialog unloaded previous dialog

[romigrabarz]

Describe the bug

I have window as MetroWindow. This window has custom BaseMetroDialog which has button which fire command. This command call another BaseMetroDialog. When I click that button, the first BaseMetroDialog has unloaded - await dialog.WaitUntilUnloadedAsync() ends and program go next line.
Something went wrong when second BaseMetroDialog goes to ShowMetroDialogAsync.

Steps to reproduce

MainWindow

<mah:MetroWindow x:Class="MahAppMetroDialog.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mah="http://metro.mahapps.com/winfx/xaml/controls"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Button Content="Open First Dialog" Click="Button_Click"/>
    </Grid>
</mah:MetroWindow>

public partial class MainWindow : MetroWindow
    {
        public MainWindow()
        {
            InitializeComponent();
        }
        private async void Button_Click(object sender, RoutedEventArgs e)
        {
            var dialog = new FirstDialog(this);
            await this.ShowMetroDialogAsync(dialog);
            Title = "FirstDialog OPEN";
            await dialog.WaitUntilUnloadedAsync();
            Title = "FirstDialog CLOSED"; //app unloaded when FirstDialog open SecodDialog
        }
    }

FirstDialog

<mah:BaseMetroDialog x:Class="MahAppMetroDialog.FirstDialog"
				   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                   xmlns:mah="http://metro.mahapps.com/winfx/xaml/controls"
                   Title="First Dialog">
    <Grid>
        <Button Content="Open Second Dialog" Click="Button_Click"/>
    </Grid>
</mah:BaseMetroDialog>

public partial class FirstDialog : BaseMetroDialog
    {
        private readonly MetroWindow ParentWindow;
        public FirstDialog(MetroWindow parentWindow)
        {
            InitializeComponent();
            ParentWindow = parentWindow;
        }
        private async void Button_Click(object sender, System.Windows.RoutedEventArgs e)
        {
            var dialog = new SecondDialog();
            await ParentWindow.ShowMetroDialogAsync(dialog);
            await dialog.WaitUntilUnloadedAsync();
        }
    }

SecondDialog

<mah:BaseMetroDialog x:Class="MahAppMetroDialog.SecondDialog"
				   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                   xmlns:mah="http://metro.mahapps.com/winfx/xaml/controls"
                   Title="Second Dialog">
</mah:BaseMetroDialog>

Expected behavior

Open another Dialog in Dialog shouldn't unloaded previous Dialog. When I close second dialog, I want go back to first dialog before its unloaded.

Actual behavior

Open another Dialog in Dialog unloaded previous dialog.

Environment

MahApps.Metro version: v2.4.9
Windows build number: Win10 21H2 [Version 19044.1706]
Visual Studio: 2019 16.8.6
Target Framework: .Net Framework (v4.7.2)

Screenshots

[punker76]

@romigrabarz This is something what you must handle self like

public partial class FirstDialog : BaseMetroDialog
{
    private TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
    private readonly MetroWindow ParentWindow;

    public FirstDialog(MetroWindow parentWindow)
    {
        InitializeComponent();
        ParentWindow = parentWindow;
    }

    private async void Button_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        var dialog = new SecondDialog();
        await ParentWindow.ShowMetroDialogAsync(dialog);
        await dialog.WaitUntilUnloadedAsync();
    }

    private void ButtonClose_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        this.tcs.TrySetResult(true);
    }

    public Task void WaitUntilClosed()
    {
        return this.tcs.Task;
    }
}

<mah:BaseMetroDialog x:Class="MahAppMetroDialog.FirstDialog"
                   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                   xmlns:mah="http://metro.mahapps.com/winfx/xaml/controls"
                   Title="First Dialog">
    <StackPanel>
        <Button Content="Open Second Dialog" Click="Button_Click"/>
        <Button Content="Close this Dialog" Click="ButtonClose_Click"/>
    </StackPanel>
</mah:BaseMetroDialog>

private async void Button_Click(object sender, RoutedEventArgs e)
{
    var dialog = new FirstDialog(this);
    await this.ShowMetroDialogAsync(dialog);
    Title = "FirstDialog OPEN";
    await dialog.WaitUntilClosed();
    Title = "FirstDialog CLOSED";
}