????? 新人剛開始學習ASP.NET MVC，若有不足之處希望能得到您的指點，不勝感激！
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?????? 先來一張項目的層級結構圖:
????? Model：模型層，主要是各種類型、枚舉以及ORM框架，框架完成數據庫和實體類的映射。項目中選用了微軟的開源ORM框架 EntityFramework 6.0 （以下簡稱EF），數據庫則選擇了微軟的輕量級數據庫SQL Server Compact 4.0本地數據庫（簡稱Compact），Compact對EF支持比較完美，又屬于文檔型數據庫，部署起來比較簡潔。
????? DAL：數據訪問層，主要是對數據庫的操作層，為業務邏輯層或表示層提供數據服務。
????? IDAL：數據訪問接口層，是數據訪問層的接口，降低耦合。
????? DALFactory：數據會話層，封裝了所有數據操作類實例的創建，將數據訪問層與業務邏輯層解耦。
????? BLL：業務邏輯層，主要負責對數據層的操作，把一些數據層的操作進行組合以完成業務的需要。
????? IBLL：業務邏輯接口層，業務邏輯層的接口，降低耦合。
????? WebApp：表現層，是一個ASP.NET MVC項目，完成具體網站的實現。
????? Common：通用層，用來存放一些工具類。
????? 下面是各個層級之間具體的實現，首先創建以 項目名.層級名 命名的各個層次，除WebApp層為ASP.NET MVC項目外，其余均創建為類庫項目。
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模型層的構建
????? 先建立模型層，新建ASP.NET 實體數據模型，關聯到已經設計好的數據庫，EF自動完成模型類的創建。
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數據訪問層的構建
????? DAL層中，我們首先需要一個方法來獲取單例的EF數據操縱上下文對象，以保證每個用戶訪問時只有使用一個上下文對象對數據庫進行操作。DbContextFactory.cs
using System.Data.Entity; using System.Runtime.Remoting.Messaging; using PMS.Model;namespace PMS.DAL {public class DbContextFactory{/// <summary>/// 負責創建EF數據操作上下文實例,必須保證線程內唯一/// </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;}} }????? 為User類創建DAL層，實現查詢、分頁查詢、增加、刪除和修改這五個基本的方法：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>/// 查詢過濾/// </summary>/// <param name="whereLamada">過濾條件Lambda表達式</param>/// <returns>實體集合</returns>public IQueryable<UserDal> LoadEntities(System.Linq.Expressions.Expression<Func<UserDal, bool>> whereLamada){return DbEntities.Set<UserDal>().Where(whereLamada);}/// <summary>/// 分頁查詢/// </summary>/// <typeparam name="TS">排序類型</typeparam>/// <param name="pageIndex">查詢的頁碼</param>/// <param name="pageSize">每頁顯示的數目</param>/// <param name="totalCount">符合條件的總行數</param>/// <param name="whereLambda">過濾條件Lambda表達式</param>/// <param name="orderbyLambda">排序Lambda表達式</param>/// <param name="isAsc">排序方向</param>/// <returns>實體集合</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>/// 刪除數據/// </summary>/// <param name="entity">待刪數據</param>/// <returns>刪除結果</returns>public bool DeleteEntity(UserDal entity){DbEntities.Entry(entity).State = EntityState.Deleted;return true;}/// <summary>/// 編輯數據/// </summary>/// <param name="entity">待編輯數據</param>/// <returns>編輯結果</returns>public bool EditEntity(UserDal entity){DbEntities.Entry(entity).State = EntityState.Modified;return true;}/// <summary>/// 添加數據/// </summary>/// <param name="entity">待添加數據</param>/// <returns>已添加數據</returns>public UserDal AddEntity(UserDal entity){entity = DbEntities.Set<UserDal>().Add(entity);return entity;} } }注：這里的增刪改操作并不即時進行，而是在封裝在數據會話層中，以實現工作單元模式，提高數據庫的操作效率。
????? 考慮到每個類都需要實現相同的數據操作，我們可以將以上方法封裝到一個泛型基類中，各類型只需要繼承泛型基類就可以實現以上方法：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>/// 查詢過濾/// </summary>/// <param name="whereLamada">過濾條件Lambda表達式</param>/// <returns>實體集合</returns>public IQueryable<T> LoadEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLamada){return DbEntities.Set<T>().Where(whereLamada);}/// <summary>/// 分頁查詢/// </summary>/// <typeparam name="TS">排序類型</typeparam>/// <param name="pageIndex">查詢的頁碼</param>/// <param name="pageSize">每頁顯示的數目</param>/// <param name="totalCount">符合條件的總行數</param>/// <param name="whereLambda">過濾條件Lambda表達式</param>/// <param name="orderbyLambda">排序Lambda表達式</param>/// <param name="isAsc">排序方向</param>/// <returns>實體集合</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>/// 刪除數據/// </summary>/// <param name="entity">待刪數據</param>/// <returns>刪除結果</returns>public bool DeleteEntity(T entity){DbEntities.Entry(entity).State = EntityState.Deleted;return true;}/// <summary>/// 編輯數據/// </summary>/// <param name="entity">待編輯數據</param>/// <returns>編輯結果</returns>public bool EditEntity(T entity){DbEntities.Entry(entity).State = EntityState.Modified;return true;}/// <summary>/// 添加數據/// </summary>/// <param name="entity">待添加數據</param>/// <returns>已添加數據</returns>public T AddEntity(T entity){entity = DbEntities.Set<T>().Add(entity);//DbEntities.SaveChanges();return entity;}} }UserDal繼承BaseDal
using PMS.IDAL; using PMS.Model;namespace PMS.DAL {public partial class UserDal : BaseDal<User>{} }
數據訪問接口層的構建
????? 然后我們建立相應的IbaseDal接口和IUserDal接口，并且使UserDal類實現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實現IUserDal接口：
public partial class UserDal : BaseDal<User>,IUserDal
數據會話層的構建
抽象工廠類AbstractFactory：
using System.Configuration; using System.Reflection; using PMS.IDAL;namespace PMS.DALFactory {public partial class AbstractFactory{//讀取保存在配置文件中的程序集名稱與命名空間名private static readonly string AssemblyPath = ConfigurationManager.AppSettings["AssemblyPath"];private static readonly string NameSpace = ConfigurationManager.AppSettings["NameSpace"];/// <summary>/// 獲取UserDal的實例/// </summary>/// <returns></returns>public static IUserDal CreateUserInfoDal(){var fullClassName = NameSpace + ".UserInfoDal";return CreateInstance(fullClassName) as IUserDal;}/// <summary>/// 通過反射獲得程序集中某類型的實例/// </summary>/// <param name="className"></param>/// <returns></returns>private static object CreateInstance(string className){var assembly = Assembly.Load(AssemblyPath);return assembly.CreateInstance(className);}} }數據會話類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>/// 工作單元模式，統一保存數據/// </summary>/// <returns></returns>public bool SaveChanges(){return Db.SaveChanges() > 0;}} }?
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業務邏輯層的構建
業務類基類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();//子類一定要實現抽象方法，以指明當前類的子類類型。 }/// <summary>/// 查詢過濾/// </summary>/// <param name="whereLambda"></param>/// <returns></returns>public IQueryable<T> LoadEntities(Expression<Func<T, bool>> whereLambda){return CurrentDal.LoadEntities(whereLambda);}/// <summary>/// 分頁/// </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>/// 刪除/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool DeleteEntity(T entity){CurrentDal.DeleteEntity(entity);return CurrentDbSession.SaveChanges();}/// <summary>/// 編輯/// </summary>/// <param name="entity"></param>/// <returns></returns>public bool EditEntity(T entity){CurrentDal.EditEntity(entity);return CurrentDbSession.SaveChanges();}/// <summary>/// 添加數據/// </summary>/// <param name="entity"></param>/// <returns></returns>public T AddEntity(T entity){CurrentDal.AddEntity(entity);CurrentDbSession.SaveChanges();return entity;}} }?
UserService類：
using PMS.IBLL; using PMS.Model;namespace PMS.BLL {public partial class UserService : BaseService<User>{public override void SetCurrentDal(){CurrentDal = CurrentDbSession.UserDal;}} }?
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業務邏輯接口層的構建
????? 直接建立對應的接口并使用UserService類實現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類實現IUserService接口:
public partial class UserService : BaseService<User>, IUserService?
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以上我們就完成了整個框架中關于User類的各層次的實現。
