c# BS程序只能运行一次(多次运行只能打开同一个程序)

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

namespace WindowsFormsApplication1
{
    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 INORMAL = 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)
            {
             
                Application.Run(new Form1());
            }
            else
            {
                HandleRunningInstance(instance);
            }
        }

        /// <summary> 
        /// 获取正在运行的实例，没有运行的实例返回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> 
        /// 显示已运行的程序。 
        /// </summary> 
        public static void HandleRunningInstance(Process instance)
        {
            ShowWindowAsync(instance.MainWindowHandle, INORMAL); 
            SetForegroundWindow(instance.MainWindowHandle);                   } 
    }
}

主要用到两个API 函数:

ShowWindowAsync 该函数设置由不同线程产生的窗口的显示状态。

SetForegroundWindow 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。