实体类//包含三层代码里需要用到的属性，传递的参数usingSystem;usingSystem.Data;usingSystem.Configuration;usingSystem.Web;usingSystem.Web.Security;usingSystem.Web.UI;usingSystem.Web.UI.WebControls;usingSystem.Web.UI.WebControls.WebParts;usingSystem.Web.UI.HtmlControls;namespacedep.model//定义命名空间其他的页面才能引用才能传递参数{publicclassDepartment{publicDepartment(){}privateint_departmentID;//字段是私有的，无法直接读取和修改publicintDepartmentID//通过封装公有的get/set方法分别读取修改{get{return_departmentID;}set{_departmentID=value;}}privatestring_departmentName;publicstringDepartmentName{get{return_departmentName;}set{_departmentName=value;}}privatestring_leaderName;publicstringLeaderName{get{return_leaderName;}set{_leaderName=value;}}privatestring_office;publicstringOffice{get{return_office;}set{_office=value;}}}}业务逻辑层的代码：usingSystem;usingSystem.Data;usingSystem.Configuration;usingSystem.Web;usingSystem.Web.Security;usingSystem.Web.UI;usingSystem.Web.UI.WebControls;usingSystem.Web.UI.WebControls.WebParts;usingSystem.Web.UI.HtmlControls;usingdep.model;//需要引用一下实体类usingdep.dal;//需要引用数据访问层usingSystem.Collections.Generic;//可以使用List<>泛型namespacedep.bll//声明的命名空间，也就是其他页面进行引用的类的名字{publicclassDepartmentBll{publicDepartmentBll(){}//这是构造方法privatereadonlyDepartmentDaldeptDal=newDepartmentDal();//声明一个dal的实例，只有声明了才能用，也就是说把抽象概念变成具体的对象publicboolinsert(Departmentdept){returndeptDal.Insert(dept);//调用数据访问层的Insert方法，通过实例调用，也就是deptDal这个实例，这是在上头实例化中声明的实例名（粗斜体）。}publicList<Department>Display(){returndeptDal.DisplayAll();//调用数据访问层的displayAll方法}}}数据访问层usingSystem;usingSystem.Data;usingSystem.Configuration;usingSystem.Web;usingSystem.Web.Security;usingSystem.Web.UI;usingSystem.Web.UI.WebControls;usingSystem.Web.UI.WebControls.WebParts;usingSystem.Web.UI.HtmlControls;usingSystem.Data.SqlClient;//用到Sqlconnection对象的时候需要引用这个！usingdep.model;//引用实体类usingSystem.Collections.Generic;//结果集需要引用才能用List<>泛型namespacedep.dal//这是这个页面定义的命名空间{publicclassDepartmentDal{stringcon;SqlConnectionc