Program.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace TaskTrayScreenChanger
{
    internal static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            const string appName = "Multi-Screen Profile Switcher";
            bool createdNew;

            var mutex = new Mutex(true, appName, out createdNew);

            if (!createdNew)
            {
                //app is already running! Exiting the application
                return;
            }


            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new TaskTrayApplicationContext());
        }
    }
}