windows窗体计算器，可实现普通计算，附带注册和登陆功能！-windows form calculator, ordinary calculation can be realized, with registration and landing function!

简单计算器的实现，适合c#初学者练习参考使用，Windows 应用程序。-The realization of a simple calculator, suitable for beginners c# reference to the use of exercises, Windows applications.