WPF main window put in background after closing a child window

Question

I have developed a sample WPF project.
Here is the main window's code-behind :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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;
using Telerik.Windows.Controls;

namespace MainWindowInBackground
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Window l_hostWindow = new Window()
            {
                Owner = System.Windows.Application.Current.MainWindow,
                WindowStartupLocation = WindowStartupLocation.CenterOwner,
                Content = "Test"
            };

            l_hostWindow.Show();

            Window l_hostWindow2 = new Window()
            {
                Owner = System.Windows.Application.Current.MainWindow,
                WindowStartupLocation = WindowStartupLocation.CenterOwner,
                Content = "Test 2"
            };

            l_hostWindow2.Show();
            l_hostWindow2.Close();

            //MessageBox.Show(this, "MessageBox", "MessageBox", MessageBoxButton.OK, MessageBoxImage.Information, MessageBoxResult.OK);
        }
    }
}

When the user clicks the button :

1. A window R1 is created and shown
2. A window R2 is created and shown
3. The R2 window is closed

I have done the following actions :

• I have launched the application. Screenshot taken after the action :

• I have clicked the button. The R1 window was displayed. Screenshot taken after the action :

• I have closed the R1 window. The main window has been automatically put in background. Screenshot taken after the action :

Can someone please explain me why the main window has been automatically put in background and how to avoid it ? Thank you in advance for your help

Answer 1

Can't tell you why it's sent to background but the way to keep it in the foreground and focused is to make it the Owner of the child Window and to call Window.Focus() method of the Parent Window when the child Window is closed...

public ChildWindow()
{
    InitializeComponent();
    Owner = Application.Current.MainWindow;
}

private void ChildWindow_OnClosed(object sender, WindowClosedEventArgs e)
{
    if (Owner == null) return;
    Owner.Focus();
}