Process[] processes = rocess.GetProcessesByName("ConDemo");

            if (processes.Length > )

            {

                MessageBox.Show("应用程序已经在运行","提示");

            }

private Mutex mutex;

this.mutex = new Mutex(true, name, out flag);//name传入的是进程名称

if (!flag)

{

      MsgBox.ShowMessage("已经启动了一个程序！");

      Process.GetCurrentProcess().Kill();

      return;

}