WinForm 限制同一个进程只能打开一次

static voidMain()
        { 
                Application.EnableVisualStyles();
                Application.SetCompatibleTextRenderingDefault(false);
                Application.Run(newfrMain()); 
        }

static voidMain()
{
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            //1.这里判定是否已经有实例在运行
            //只运行一个实例
            Process instance =RunningInstance();
            if (instance == null)
            {
                //1.1 没有实例在运行
                Application.Run(newFrMain()); 
            }
            else{
                //1.2 已经有一个实例在运行
HandleRunningInstance(instance);
            }
 }


//2.在进程中查找是否已经有实例在运行
private staticProcess RunningInstance()
  {
            Process current =Process.GetCurrentProcess();
            Process[] processes =Process.GetProcessesByName(current.ProcessName);
            //遍历与当前进程名称相同的进程列表
            foreach (Process process inprocesses)
            {
                //如果实例已经存在则忽略当前进程
                if (process.Id !=current.Id)
                {
                    //保证要打开的进程同已经存在的进程来自同一文件路径
                    if (Assembly.GetExecutingAssembly().Location.Replace("/", "\") ==current.MainModule.FileName)
                    {
                        //返回已经存在的进程
                        returnprocess;
                    }
                }
            }
            return null;
  }


//3.已经有了就把它激活，并将其窗口放置最前端
private static voidHandleRunningInstance(Process instance)
  {
            ShowWindowAsync(instance.MainWindowHandle, 1); //调用api函数，正常显示窗口
            SetForegroundWindow(instance.MainWindowHandle); //将窗口放置最前端
}
[DllImport("User32.dll")]
  private static extern bool ShowWindowAsync(System.IntPtr hWnd, intcmdShow);
  [DllImport("User32.dll")]
  private static extern bool SetForegroundWindow(System.IntPtr hWnd);