WPF mutex single instance

private static Mutex mtx = null;
public MainWindow()
{
    bool isCreateNew;
    string appName = System.IO.Path.GetFileName(System.Reflection.Assembly.GetExecutingAssembly().Location);
    mtx = new Mutex(true, appName, out isCreateNew);
    if(!isCreateNew)
    {
        MessageBox.Show($"The app {appName} is running!", "Single Instance", MessageBoxButton.OK);
        this.Close();
    }
    InitializeComponent();
}

//

//xaml
<Window x:Class="WpfApp430.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:WpfApp430"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <TextBlock HorizontalAlignment="Stretch"
                   VerticalAlignment="Stretch"
                   Text="Single Instance"
                   FontSize="100"/>
    </Grid>
</Window>



//.xaml.cs
using System;
using System.Collections.Generic;
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 WpfApp430
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private static Mutex mtx = null;
        public MainWindow()
        {
            bool isCreateNew;
            string appName = System.IO.Path.GetFileName(System.Reflection.Assembly.GetExecutingAssembly().Location);
            mtx = new Mutex(true, appName, out isCreateNew);
            if(!isCreateNew)
            {
                MessageBox.Show($"The app {appName} is running!", "Single Instance", MessageBoxButton.OK);
                this.Close();
            }
            InitializeComponent();
        }
    }
}