winform激活窗口

 [System.Runtime.InteropServices.DllImportAttribute("User32.dll")]
        private static extern bool ShowWindowAsync(IntPtr hWnd, int cmdShow);
        /// 

        /// 该函数将创建指定窗口的线程设置到前台，并且激活该窗口。键盘输入转向该窗口，并为用户改各种可视的记号。系统给创建前台窗口的线程分配的权限稍高于其他线程。
        /// 
        /// 将被激活并被调入前台的窗口句柄。
        /// 如果窗口设入了前台，返回值为非零；如果窗口未被设入前台，返回值为零。
        [System.Runtime.InteropServices.DllImportAttribute("User32.dll")]
        private static extern bool SetForegroundWindow(IntPtr hWnd);
        private const int WS_SHOWNORMAL = 1;
        private const int WS_SHOWMAXIMIZED = 3;


        public static System.Diagnostics.Process RunningInstance()
        {
            
            System.Diagnostics.Process[] processes = System.Diagnostics.Process.GetProcessesByName("RS5000");
            foreach (System.Diagnostics.Process process in processes)
            {
                return process;

            }
            return null;
        }

        public static void HandleRunningInstance(System.Diagnostics.Process instance)
        {
            ShowWindowAsync(instance.MainWindowHandle, WS_SHOWMAXIMIZED); //显示，可以注释掉
            SetForegroundWindow(instance.MainWindowHandle);            //放到前端
        }
         public static void Main()
        {
               System.Diagnostics.Process instance = RunningInstance();
                if (instance != null)
                {
                    HandleRunningInstance(instance);
                }
        }