Program

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
namespace CalendarGenerationTool
{
    static class Program
    {
        [DllImport("user32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        [DllImport("user32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
        [DllImport("user32.dll")]
        private static extern bool IsIconic(IntPtr hWnd);
        private const int SW_RESTORE = 9;
        /// <summary>
        /// c# 进程窗口显示并前置
        /// </summary>
        public static void RaiseOtherProcess()
        {
            Process proc = Process.GetCurrentProcess();
            Process.GetProcesses();
            foreach (Process otherProc in Process.GetProcessesByName(proc.ProcessName))
            {
                //ignore "this" process
                if (proc.Id != otherProc.Id)
                {
                    // Found a "same named process".
                    // Assume it is the one we want brought to the foreground.
                    // Use the Win32 API to bring it to the foreground.
                    IntPtr hWnd = otherProc.MainWindowHandle;
                    if (IsIconic(hWnd))
                    {
                        ShowWindowAsync(hWnd, 9);
                    }
                    SetForegroundWindow(hWnd);
                    break;
                }
            }
        }
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Mutex instance = new Mutex(true, "MainFrm", out bool createdNew);
            if (createdNew)
            {
                Application.Run(new MainFrm());
                instance.ReleaseMutex();
                //如果需要窗体重启，并出现问题，将这句改为
                //instance.Dispose();
            }
            else
            {
                RaiseOtherProcess();
                Application.Exit();
            }
        }
    }
}