通过重载CEdit类的onchar()函数，实现文本框的限制输入，可根据的自己的需求写限制条件-By overloading CEdit class onchar () function to achieve a text box to limit the importation, according to the needs of their own to write constraints

创建可一个新类 继承于CEDIT 重写了ONCHAR函数，提供了一种改变编辑框输入文本内容的限制。-Create a new class inherits from CEDIT rewriting the ONCHAR function, provides a way to change the edit box to enter text content restrictions.