WPF ShowDialog与另一个活动窗口

Question

When my MainWindow starts, I automatically show a 2nd "CountdownWindow". The CountdownWindow is TopMost.

While both the Main and Countdown windows are shown the user can click a button to launch a 3rd Modal Window with ShowDialog.

While the Dialog is active, I would like the user to be able to also interact with the topmost CountdownWindow (ie, minimize, maximize, close it or move it around), however this is not possible.

Would launching the Dialog window from a separate process or a separate thread solve this problem?

Here are the relevant parts of my code if you need it

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

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        var dialogWindow = new DialogWindow();
        dialogWindow.ShowDialog();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        var countDownWindow = new CountdownWindow();
        countDownWindow.Owner = this;
        countDownWindow.Show();
    }
}

<Window x:Class="WpfTestBase.CountdownWindow"
    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:WpfTestBase"
    mc:Ignorable="d"
    Topmost="True"
    Title="CountdownWindow TopMost=True" Height="300" Width="400">
<Grid>

</Grid>

Answer 1

Instead of Dialog.ShowDialog() why don't you just set the Dialog.Owner = MainWindow, then Dialog.Show()? It will then stay on top of the main window, but will not block the main thread as it does with ShowDialog(). The whole point of ShowDialog is to be modal, and block the main UI thread.