C# WinForm 判断程序是否已经在运行，且只允许运行一个实例

static  class  Program
{

   ///

  /// 应用程序的主入口点。
  ///
  [STAThread]
  static  void  Main()
  {
    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( new  frmMain());
    }
    else
    {
      //1.2 已经有一个实例在运行
      HandleRunningInstance(instance);
    }

    //Application.Run(new frmMain());
  }

  //2.在进程中查找是否已经有实例在运行
  #region 确保程序只运行一个实例
  private  static  Process 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  in  processes)
    {
      //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
          return  process;
        }
      }
    }
    return  null ;
  }
  //3.已经有了就把它激活，并将其窗口放置最前端
  private  static  void  HandleRunningInstance(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,  int  cmdShow);
  [DllImport( "User32.dll" )]
  private  static  extern  bool  SetForegroundWindow(System.IntPtr hWnd);
  #endregion
}


转载 http://www.jb51.net/article/82124.htm