C# running program always keeps only one open

Method 1: If the program is already running, display the running program directly

//Introduce 3 namespaces

using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Reflection;

 

namespace MyWindow
{
    static class Program
    {
        [DllImport("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        [DllImport("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        private const int WS_SHOWNORMAL = 1;
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            Process instance = RunningInstance();
            if (instance == null)
            {
                Form1 frm = new Form1();
                Application.Run(new Form1());
            }
            else
            {
                HandleRunningInstance(instance);
            }
        }

        /// <summary>
        /// Get the running instance, the instance that is not running returns null;
        /// </summary>
        public static Process RunningInstance()
        {             Process current = Process.GetCurrentProcess();             Process[] processes = Process.GetProcessesByName(current.ProcessName);             foreach (Process process in processes)             {                 if (process.Id != current.Id)                 {                     if (Assembly.GetExecutingAssembly().Location.Replace("/", "\\") == current.MainModule.FileName)                     {                         return process;                     }                 }











            }
            return null;
        }

        /// <summary>
        /// Display the running programs.
        /// </summary>
        public static void HandleRunningInstance(Process instance)
        {             ShowWindowAsync(instance.MainWindowHandle, WS_SHOWNORMAL); //Display, you can comment out             SetForegroundWindow(instance.MainWindowHandle); // Put it on the front end         }     } }

 

Method 2: If the program is already running, it only prompts "there is a program running"
            System.Threading.Mutex mutex;
            bool isNew;
            mutex = new System.Threading.Mutex(true, "myproject", out isNew);
            if (isNew)
            {                 Application.EnableVisualStyles();                 Application.SetCompatibleTextRenderingDefault(false);                 Application.Run(new Form1());             }             else             {                 MessageBox.Show("This program is already running");             }