一本讲解CSharp三层架构的书籍，系统的分析了三层中每层的功能和实现！-CSharp on a three-tier system of books, a systematic analysis of each of the three functions and achieve!

本系统主要实现了支持多条件查询、批量填写进货单及销售单、与代理商和供应商往来账本明细，绝不存在假账、漏账、差账等情况、图表分析月销售状况、当外界环境（停电、网络病毒）干扰本系统时，系统可以自动保护原始数据的安全、强大的报表打印等功能。-This system is mainly implemented to support multi-criteria query, bulk fill Jinhuo Dan and sales orders, and agents and suppliers e