一直想用O/R M的模式去开应用系统；但在。NET下又没有成熟的产品，nhibernate虽然不错但结构比较复杂，如果出现问题维护起来也比较麻烦。所以打算自己编写这样一个组件，在使用、维护和扩展方面的都比较容易把握；对项目的后期维护也比较有利。组件功能上也远比不上nhibernate,只实现了单表和视图的映射操作、查询对象化等功能。在设计的过程也参考了nhibernate的设计方式，毕竟nhibernate的设计不错可以直接拿过来使用。根据自己的情况修改一下就可以了。

在设计时第一个考虑的问题就是组件对多类型数据库的支持，所以针对数据库提供者提取接口；在设计这个接口时nhibernate给我带来很大的启发；可以说是直接引用了它的设计原理。当数据库提供者接口完成后，就可以针对这个接口做数据库处理的工作了。

IExpression

类和数据库的关系映射

using System;

namespace NorthWind.Entitys

{

     /// <summary>

     /// Employees

     /// </summary>

     public class Employees

     {

         public Employees()

         {

              //

              // TODO: 在此处添加构造函数逻辑

              //

         }

         public const string F_EmployeeID="EmployeeID";

         private Int32 mEmployeeID;

         /// <summary>

         /// [int identity]

         /// </summary>

         public Int32 EmployeeID

         {

              get

              {

                   return mEmployeeID;

              }

              set

              {

                   mEmployeeID = value;

              }

         }

         public const string F_LastName="LastName";

         private String mLastName;

         /// <summary>

         /// [nvarchar]

         /// </summary>

         public String LastName

         {

              get

              {

                   return mLastName;

              }

              set

              {

                   mLastName = value;

              }

         }

         public const string F_FirstName="FirstName";

         private String mFirstName;

         /// <summary>

         /// [nvarchar]

         /// </summary>

         public String FirstName

         {

              get

              {

                   return mFirstName;

              }

              set

              {

                   mFirstName = value;

              }

         }

          ………………..

         ………………..

       <?xml version="1.0" encoding="utf-8" ?>

<class name="NorthWind.Entitys.Employees,NorthWind.Entitys" table="Employees">

     <id name="EmployeeID" column="EmployeeID" value="SELECT @@IDENTITY ,false"/>

     <property name="LastName" column="LastName"/>

     <property name="FirstName" column="FirstName"/>

     <property name="Title" column="Title"/>

     <property name="TitleOfCourtesy" column="TitleOfCourtesy"/>

     <property name="BirthDate" column="BirthDate"/>

     <property name="HireDate" column="HireDate"/>

     <property name="Address" column="Address"/>

     <property name="City" column="City"/>

     <property name="Region" column="Region"/>

     <property name="PostalCode" column="PostalCode"/>

     <property name="Country" column="Country"/>

     <property name="HomePhone" column="HomePhone"/>

     <property name="Extension" column="Extension"/>

     <property name="Photo" column="Photo"/>

     <property name="Notes" column="Notes"/>

     <property name="ReportsTo" column="ReportsTo"/>

     <property name="PhotoPath" column="PhotoPath"/>

</class>

组件的使用

<configSections>

         <section name="dataconfig" type="HFSoft.Data.DataConfigSectionHandler, HFSoft.Data, Version=0.9.1.0, Culture=neutral, PublicKeyToken=null" />

</configSections>

<dataconfig>

         <DriverType value="HFSoft.Data.SqlDriver, HFSoft.Data, Version=0.9.1.0, Culture=neutral, PublicKeyToken=null"/>

         <ConnectionString  value="data source=.;initial catalog=northwind;user id=sa;pwd=;"/>

         <MappingAssemblys>

              <Assembly value="NorthWind.Entitys"/>

         </MappingAssemblys>

         <CacheCommands default="3"/>

</dataconfig>

添加一条雇员信息

HFSoft.Data.MappingContainer mapContainer = HFSoft.Data.MappingContainer.ConfigContainer;

                   using(HFSoft.Data.IDataSession session = mapContainer.OpenSession())

                   {

                       session.Open();

                       NorthWind.Entitys.Employees emp = new NorthWind.Entitys.Employees();

                       emp.ReportsTo = 3;

                       emp.FirstName ="fan";

                       emp.LastName = "henry";

                       emp.Photo = new byte[0];

                       emp.HireDate = DateTime.Parse("2002-12-31");

                       emp.BirthDate = DateTime.Parse("1979-1-28");

                       emp.City ="广州";

                       emp.Country ="中国";

                       session.Save(emp);

                       MessageBox.Show(emp.EmployeeID.ToString());

                      

                   }

获取所有雇员信息

using(HFSoft.Data.IDataSession session = mapContainer.OpenSession())

                   {

                       session.Open();

System.Collections.IList  myDS = session.List(typeof(NorthWind.Entitys.Employees),null);

                       this.dataGrid1.DataSource = myDS;

                   }

多条件查询（雇员编号大于等于3并且小于等于10或者姓包含fan）

HFSoft.Data.Expression expression = new HFSoft.Data.Expression();

expression.Add(new HFSoft.Data.RtEqExpression(NorthWind.Entitys.Employees.F_EmployeeID,3));

expression.Add(new HFSoft.Data.LeEqExpression(NorthWind.Entitys.Employees.F_EmployeeID,10));

expression.Add(HFSoft.Data.UintType.Or,new HFSoft.Data.LikeExpression(NorthWind.Entitys.Employees.F_FirstName,"fan%"));

                   using(HFSoft.Data.IDataSession session = mapContainer.OpenSession())

                   {

                       session.Open();

System.Collections.IList  myDS = session.List(typeof(NorthWind.Entitys.Employees),expression);

                       this.dataGrid1.DataSource = myDS;

                   }

获取雇员信息并修改

using(HFSoft.Data.IDataSession session = mapContainer.OpenSession())

                   {

                       session.Open();

NorthWind.Entitys.Employees emp = (NorthWind.Entitys.Employees)session.Load(typeof(NorthWind.Entitys.Employees),41);

                       emp.FirstName ="kfc";

                       session.Update(emp);

                      

                   }

     组件为了提高效率，增加了缓存机制。可以通过配置文件制定对插入数据、修改数据的命令对象进行缓存的数量。当组件需要调用对象的插入命令时就会从缓存中找，当找不到的情况下才创建相关命令对象，这样会减少创建所带来的性能问题；同样缓存会占用相应的内存资源。组件现在还决少查询命令对象、数据集、实体对象的缓存。实体对象缓存比较复杂，中间还存在着和数据库信息同步、频繁锁的问题；还没有想到较好的解决方法，暂时没有打算把实体缓存集成到组件中。