C# Mutex to make sure only one unique application instance started

static void MutexDemo2()
        {
            string assName = Assembly.GetEntryAssembly().FullName;
            bool createdNew;
            using (var mutex = new Mutex(false, assName, out createdNew))
            {
                if (!createdNew)
                {
                    Console.WriteLine("The app in running!");
                    Console.ReadLine();
                }
                else
                {
                    Console.WriteLine("Welcome!");
                    Console.ReadLine();
                }
            }
        }

using System;
using System.Threading.Tasks;
using System.Reflection;
using System.Threading;
using System.Windows.Forms;

 static void Main(string[] args)
        {
            MutexDemoBool();
            Console.ReadLine();
        }

        static void MutexDemo()
        {
            string assemblyName = Assembly.GetEntryAssembly().FullName;
            var mutex = new Mutex(false, assemblyName);

            if (!mutex.WaitOne(, true))
            {
                MessageBox.Show("Unable to run multiple instances of this program.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                Console.WriteLine("Welcome");
                Console.ReadLine();
            }
        }

        static void MutexDemoBool()
        {
            string assemblyName = Assembly.GetEntryAssembly().FullName;
            bool isFirstInstance;
            var mutex = new Mutex(false, assemblyName,out isFirstInstance);
            if(!isFirstInstance)
            {
                MessageBox.Show("Unable to run multiple instances of this program.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else
            {
                Console.WriteLine("Welcome");
                Console.ReadLine();
            }
        }