How to run single instance of an application using Mutex?

App.xaml.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;

namespace WPFSingleInstanceApplication
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        private static Mutex mutex = null;
        protected override void OnStartup(StartupEventArgs e)
        {
            bool isFirstInstance;
            mutex = new Mutex(true, "MyWPFApp", out isFirstInstance);
            if (isFirstInstance)
            {
                MessageBox.Show("Welcome, Running first instance of MyWPFApp", "Info");
                MainWindow window = new MainWindow();
                window.Show();
            }
            else
            {
                MessageBox.Show("One instance of MyWPFApp is already running.", "Info");
                Application.Current.Shutdown();
            }

            base.OnStartup(e);
        }
    }
}

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace SingleInstanceApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            bool isFirstInstance;
            using (Mutex mutex = new Mutex(true, "MyApp", out isFirstInstance))
            {
                if (isFirstInstance)
                {
                    Console.WriteLine("Welcome, Running first instance of MyApp.");
                    Console.Read();
                }
                else
                {
                    Console.WriteLine("One instance of MyApp is already running.");
                    Console.Read();
                }
            }
        }
    }
}

Program1.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace SingleInstanceApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            //get process count of running application
            if (System.Diagnostics.Process.GetProcessesByName(
                System.IO.Path.GetFileNameWithoutExtension(
                    System.Reflection.Assembly.GetEntryAssembly().Location)).Count() > 1)
            {
                Console.WriteLine("One instance is already running so closing this instance.");
                Console.Read();
                System.Diagnostics.Process.GetCurrentProcess().Kill();
            }
            else
            {
                Console.WriteLine("Welcome, Running first instance.");
                Console.Read();
            }
        }
    }
}