采用互斥体的方法，防止程序多次运行，App.PreIntance只能判断当前目录是否有多个实例运行，本程序可以将exe拷贝到任何目录，但只能运行一个实例。-Mutex methods used to prevent the program running on many occasions, App.PreIntance only the current directory to determine whether there are multiple instances running, th