新人刚开始学习ASP.NET MVC，若有不足之处希望能得到您的指点，不胜感激！
先来一张项目的层级结构图:
Model：模型层，主要是各种类型、枚举以及ORM框架，框架完成数据库和实体类的映射。项目中选用了微软的开源ORM框架 EntityFramework 6.0 （以下简称EF），数据库则选择了微软的轻量级数据库SQL Server Compact 4.0本地数据库（简称Compact），Compact对EF支持比较完美，又属于文档型数据库，部署起来比较简洁。
DAL：数据访问层，主要是对数据库的操作层，为业务逻辑层或表示层提供数据服务。
IDAL：数据访问接口层，是数据访问层的接口，降低耦合。
DALFactory：数据会话层，封装了所有数据操作类实例的创建，将数据访问层与业务逻辑层解耦。
BLL：业务逻辑层，主要负责对数据层的操作，把一些数据层的操作进行组合以完成业务的需要。
IBLL：业务逻辑接口层，业务逻辑层的接口，降低耦合。
WebApp：表现层，是一个ASP.NET MVC项目，完成具体网站的实现。
Common：通用层，用来存放一些工具类。
下面是各个层级之间具体的实现，首先创建以 项目名.层级名 命名的各个层次，除WebApp层为ASP.NET MVC项目外，其余均创建为类库项目。
模型层的构建
先建立模型层，新建ASP.NET 实体数据模型，关联到已经设计好的数据库，EF自动完成模型类的创建。
数据访问层的构建
DAL层中，我们首先需要一个方法来获取单例的EF数据操纵上下文对象，以保证每个用户访问时只有使用一个上下文对象对数据库进行操作。DbContextFactory.cs
using System.Data.Entity; using System.Runtime.Remoting.Messaging; using PMS.Model;namespace PMS.DAL {public class DbContextFactory{/// <summary>/// 负责创建EF数据操作上下文实例,必须保证线程内唯一/// </summary>public static DbContext CreateContext(){DbContext dbContext = (DbContext)CallContext.GetData("dbContext");if (dbContext != null) return dbContext;dbContext = new PMSEntities();CallContext.SetData("dbContext", dbContext);return dbContext;}} }为User类创建DAL层，实现查询、分页查询、增加、删除和修改这五个基本的方法：UserDAL.cs
using System; using System.Data.Entity; using System.Linq; using PMS.IDAL;namespace PMS.DAL {public partial class UserDal{public DbContext DbEntities = DbContextFactory.CreateContext();/// <summary>/// 查询过滤/// </summary>/// <param name="whereLamada">过滤条件Lambda表达式</param>/// <returns>实体集合</returns>public IQueryable<UserDal> LoadEntities(System.Linq.Expressions.Expression<Func<UserDal, bool>> whereLamada){return DbEntities.Set<UserDal>().Where(whereLamada);}/// <summary>/// 分页查询/// </summary>/// <typeparam name="TS">排序类型</typeparam>/// <param name="pageIndex">查询的页码</param>/// <param name="pageSize">每页显示的数目</param>/// <param name="totalCount">符合条件的总行数</param>/// <param name="whereLambda">过滤条件Lambda表达式</param>/// <param name="orderbyLambda">排序Lambda表达式</param>/// <param name="isAsc">排序方向</param>/// <returns>实体集合</returns>public IQueryable<UserDal> LoadPageEntities<TS>(int pageIndex, int pageSize, out int totalCount, System.Linq.Expressions.Expression<Func<UserDal, bool>> whereLambda, System.Linq.Expressions.Expression<Func<UserDal, TS>> orderbyLambda, bool isAsc){var temp = DbEntities.Set<UserDal>().Where(whereLambda);totalCount = temp.Count();temp = isAsc ? temp.OrderBy(orderbyLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize) : temp.OrderByDescending(orderbyLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize);return temp;}/// <summary>/// 删除数据/// </summary>/// <param name="entity">待删数据</param>/// <returns>删除结果</returns>public bool DeleteEntity(UserDal entity){DbEntities.Entry(entity).State = EntityState.Deleted;return true;}/// <summary>/// 编辑数据/// </summary>/// <param name="entity">待编辑数据</param>/// <returns>编辑结果</returns>public bool EditEntity(UserDal entity){DbEntities.Entry(entity).State = EntityState.Modified;return true;}/// <summary>/// 添加数据/// </summary>/// <param name="entity">待添加数据</param>/// <returns>已添加数据</returns>public UserDal AddEntity(UserDal entity){entity = DbEntities.Set<UserDal>().Add(entity);return entity;} } }注：这里的增删改操作并不即时进行，而是在封装在数据会话层中，以实现工作单元模式，提高数据库的操作效率。
考虑到每个类都需要实现相同的数据操作，我们可以将以上方法封装到一个泛型基类中，各类型只需要继承泛型基类就可以实现以上方法：BaseDal.cs
using System; using System.Data.Entity; using System.Linq;namespace PMS.DAL {public class BaseDal<T> where T:class ,new(){public DbContext DbEntities = DbContextFactory.CreateContext();/// <summary>/// 查询过滤/// </summary>/// <param name="whereLamada">过滤条件Lambda表达式</param>/// <returns>实体集合</returns>public IQueryable<T> LoadEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLamada){return DbEntities.Set<T>().Where(whereLamada);}/// <summary>/// 分页查询/// </summary>/// <typeparam name="TS">排序类型</typeparam>/// <param name="pageIndex">查询的页码</param>/// <param name="pageSize">每页显示的数目</param>/// <param name="totalCount">符合条件的总行数</param>/// <param name="whereLambda">过滤条件Lambda表达式</param>/// <param name="orderbyLambda">排序Lambda表达式</param>/// <param name="isAsc">排序方向</param>/// <returns>实体集合</returns>public IQueryable<T> LoadPageEntities<TS>(int pageIndex, int pageSize, out int totalCount, System.Linq.Expressions.Expression<Func<T, bool>> whereLambda, System.Linq.Expressions.Expression<Func<T, TS>> orderbyLambda, bool isAsc){var temp = DbEntities.Set<T>().Where(whereLambda);totalCount = temp.Count();temp = isAsc ? temp.OrderBy(orderbyLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize) : temp.OrderByDescending(orderbyLambda).Skip((pageIndex - 1) * pageSize).Take(pageSize);return temp;}/// <summary>/// 删除数据/// </summary>/// <param name="entity">待删数据</param>/// <returns>删除结果</returns>public bool DeleteEntity(T entity){DbEntities.Entry(entity).State = EntityState.Deleted;return true;}/// <summary>/// 编辑数据/// </summary>/// <param name="entity">待编辑数据</param>/// <returns>编辑结果</returns>public bool EditEntity(T entity){DbEntities.Entry(entity).State = EntityState.Modified;return true;}/// <summary>/// 添加数据/// </summary>/// <param name="entity">待添加数据</param>/// <returns>已添加数据</returns>public T AddEntity(T entity){entity = DbEntities.Set<T>().Add(entity);//DbEntities.SaveChanges();return entity;}} }UserDal继承BaseDal
using PMS.IDAL; using PMS.Model;namespace PMS.DAL {public partial class UserDal : BaseDal<User>{} }
数据访问接口层的构建
然后我们建立相应的IbaseDal接口和IUserDal接口，并且使UserDal类实现IUserDal接口
IBaseDal：
using System; using System.Linq;namespace PMS.IDAL {public interface IBaseDal<T> where T:class,new(){IQueryable<T> LoadEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLamada);IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount,System.Linq.Expressions.Expression<Func<T, bool>> whereLambda,System.Linq.Expressions.Expression<Func<T, s>> orderbyLambda, bool isAsc);bool DeleteEntity(T entity);bool EditEntity(T entity);T AddEntity(T entity);} }IUserDal：
using PMS.Model;namespace PMS.IDAL {public partial interface IUserDal:IBaseDal<User>{} }UserDal实现IUserDal接口：
public partial class UserDal : BaseDal<User>,IUserDal
数据会话层的构建
抽象工厂类AbstractFactory：
using System.Configuration; using System.Reflection; using PMS.IDAL;namespace PMS.DALFactory {public partial class AbstractFactory{//读取保存在配置文件中的程序集名称与命名空间名private static readonly string AssemblyPath = ConfigurationManager.AppSettings["AssemblyPath"];private static readonly string NameSpace = ConfigurationManager.AppSettings["NameSpace"];/// <summary>/// 获取UserDal的实例/// </summary>/// <returns></returns>public static IUserDal CreateUserInfoDal(){var fullClassName = NameSpace + ".UserInfoDal";return CreateInstance(fullClassName) as IUserDal;}/// <summary>/// 通过反射获得程序集中某类型的实例/// </summary>/// <param name="className"></param>/// <returns></returns>private static object CreateInstance(string className){var assembly = Assembly.Load(AssemblyPath);return assembly.CreateInstance(className);}} }数据会话类DbSession：
using System.Data.Entity; using PMS.IDAL; using PMS.DAL;namespace PMS.DALFactory {public partial class DbSession:IDbSession{public DbContext Db{get { return DbContextFactory.CreateContext(); }}private IUserDal _userDal;public IUserDal UserDal{get { return _userDal ?? (_userDal = AbstractFactory.CreateUserInfoDal()); }set { _userDal = value; }}/// <summary>/// 工作单元模式，统一保存数据/// </summary>/// <returns></returns>public bool SaveChanges(){return Db.SaveChanges() > 0;}} }
业务逻辑层的构建
业务类基类BaseService
using System; using System.Linq; using System.Linq.Expressions; using PMS.DALFactory; using PMS.IDAL;namespace PMS.BLL {public abstract class BaseService<T> where T:class,new(){public IDbSession CurrentDbSession{get{return new DbSession();}}public IBaseDal<T> CurrentDal { get; set; }public abstract void SetCurrentDal();public BaseService(){SetCurrentDal();//子类一定要实现抽象方法，以指明当前类的子类类型。 }/// <summary>/// 查询过滤/// </summary>/// <param name="whereLambda"></param>/// <returns></returns>public IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda){return CurrentDal.LoadEntities(whereLambda);}/// <summary>/// 分页/// </summary>/// <typeparam name="s"></typeparam>/// <param name="pageIndex"></param>/// <param name="pageSize"></param>/// <param name="totalCount"></param>/// <param name="whereLambda"></param>/// <param name="orderbyLambda"></param>/// <param name="isAsc"></param>/// <returns></returns>public IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount, Expression<Func<T, bool>> whereLambda,Expression<Func<T, s>> orderbyLambda, bool isAsc){return CurrentDal.LoadPageEntities<s>(pageIndex, pageSize, out totalCount, whereLambda, orderbyLambda, isAsc);}/// <summary>/// 删除/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool DeleteEntity(T entity){CurrentDal.DeleteEntity(entity);return CurrentDbSession.SaveChanges();}/// <summary>/// 编辑/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool EditEntity(T entity){CurrentDal.EditEntity(entity);return CurrentDbSession.SaveChanges();}/// <summary>/// 添加数据/// </summary>/// <param name="entity"></param>/// <returns></returns>public T AddEntity(T entity){CurrentDal.AddEntity(entity);CurrentDbSession.SaveChanges();return entity;}} }
UserService类：
using PMS.IBLL; using PMS.Model;namespace PMS.BLL {public partial class UserService : BaseService<User>{public override void SetCurrentDal(){CurrentDal = CurrentDbSession.UserDal;}} }
业务逻辑接口层的构建
直接建立对应的接口并使用UserService类实现IUserService接口
IBaseService接口：
using System; using System.Linq; using System.Linq.Expressions; using PMS.IDAL;namespace PMS.IBLL {public interface IBaseService<T> where T : class,new(){IDbSession CurrentDbSession { get; }IBaseDal<T> CurrentDal { get; set; }void SetCurrentDal();IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda);IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount,Expression<Func<T, bool>> whereLambda,Expression<Func<T, s>> orderbyLambda, bool isAsc);bool DeleteEntity(T entity);bool EditEntity(T entity);T AddEntity(T entity);} }IUserService接口:
using PMS.Model;namespace PMS.IBLL {public partial interface IUserService:IBaseService<User>{} }使用UserService类实现IUserService接口:
public partial class UserService : BaseService<User>, IUserService
以上我们就完成了整个框架中关于User类的各层次的实现。
