EF--封装三层架构IOC

• 为什么分层？

不分层封装的话，下面的代码就是上端直接依赖于下端，也就是UI层直接依赖于数据访问层，分层一定要依赖抽象，满足依赖倒置原则，所以我们要封装，要分层

下面这张图和传统的三层略有不同，不同之处在于，UI层不直接依赖于业务逻辑层，而是UI层依赖于业务逻辑抽象层IBLL，业务逻辑层不直接依赖于数据访问层，而是业务逻辑层依赖于数据访问抽象层IDAL

{
    SchoolDBEntities dbContext = new SchoolDBEntities();
    dbContext.Set<Student>().Where(s=>s.Student_ID == "");
}

• 封装分层

1、David.General.EF.Bussiness.Interface（IBLL--业务逻辑抽象层）

继承IDisposable的目的是为了可以使用using，是为了释放Context

IBaseService相当于上图的IBLL（业务逻辑抽象层），DAL已经不存在了，因为EF已经取代了DAL层

namespace David.General.EF.Bussiness.Interface
{
    public interface IBaseService : IDisposable//可以使用using，是为了释放Context
    {
        #region Query
        /// <summary>
        /// 根据id主键查询实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        T Find<T>(object id) where T : class;

        /// <summary>
        /// 提供对单表的查询
        /// 不推荐对外直接开放
        ///IQueryable支持表达式目录树
        /// </summary>
        /// <returns>IQueryable类型集合</returns>
        [Obsolete("尽量避免使用，using 带表达式目录树的 代替")]
        IQueryable<T> Set<T>() where T : class;

        /// <summary>
        /// 查询，传入表达式目录树
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="funcWhere">表达式目录树</param>
        /// <returns>IQueryable类型集合</returns>
        IQueryable<T> Query<T>(Expression<Func<T, bool>> funcWhere) where T : class;

        /// <summary>
        /// 分页查询
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="S"></typeparam>
        /// <param name="funcWhere"></param>
        /// <param name="pageSize"></param>
        /// <param name="pageIndex"></param>
        /// <param name="funcOrderby"></param>
        /// <param name="isAsc"></param>
        /// <returns></returns>
        PageResult<T> QueryPage<T, S>(Expression<Func<T, bool>> funcWhere, int pageSize, int pageIndex, Expression<Func<T, S>> funcOrderby, bool isAsc = true) where T : class;
        #endregion

        #region Add
        /// <summary>
        /// 新增数据
        /// </summary>
        /// <param name="t"></param>
        /// <returns>返回带主键的实体</returns>
        T Insert<T>(T t) where T : class;

        /// <summary>
        /// 新增数据
        /// 多条sql 一个连接，事务插入
        /// </summary>
        /// <param name="tList"></param>
        IEnumerable<T> Insert<T>(IEnumerable<T> tList) where T : class;
        #endregion

        #region Update
        /// <summary>
        /// 更新数据
        /// </summary>
        /// <param name="t"></param>
        void Update<T>(T t) where T : class;

        /// <summary>
        /// 更新数据
        /// </summary>
        /// <param name="tList"></param>
        void Update<T>(IEnumerable<T> tList) where T : class;
        #endregion

        #region Delete
        /// <summary>
        /// 根据主键删除数据
        /// </summary>
        /// <param name="t"></param>
        void Delete<T>(int Id) where T : class;

        /// <su+mary>
        /// 删除数据
        /// </summary>
        /// <param name="t"></param>
        void Delete<T>(T t) where T : class;

        /// <summary>
        /// 删除数据
        /// </summary>
        /// <param name="tList"></param>
        void Delete<T>(IEnumerable<T> tList) where T : class;
        #endregion

        #region Other
        /// <summary>
        /// 立即保存全部修改
        /// 把增/删的savechange给放到这里，是为了保证事务的
        /// </summary>
        void Commit();

        /// <summary>
        /// 执行sql 返回集合
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        IQueryable<T> ExcuteQuery<T>(string sql, SqlParameter[] parameters) where T : class;

        /// <summary>
        /// 执行sql，无返回
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        void Excute<T>(string sql, SqlParameter[] parameters) where T : class;
        #endregion
    }
}

public class PageResult<T>
{
    public int TotalCount { get; set; }
    public int PageIndex { get; set; }
    public int PageSize { get; set; }
    public List<T> DataList { get; set; }
}

2、David.General.EF.Bussiness.Service（业务逻辑实现层）

namespace David.General.EF.Bussiness.Service
{
    public class BaseService : IBaseService
    {
        #region Identity
        /// <summary>
        /// protected--保证只有子类可以看得见
        /// { get; private set; }--保证只有子类可以获取，子类不能修改，只有自己可以修改
        /// </summary>
        protected DbContext Context { get; private set; }

       /// <summary>
        /// 构造函数注入
        /// 一个请求一个，不能全局一个，应该一个实例一个
        /// </summary>
        /// <param name="context"></param>
        public BaseService(DbContext context)
        {
            this.Context = context;
        }
        #endregion Identity

        #region Query
        /// <summary>
        /// 通过Id得到实体
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="id"></param>
        /// <returns></returns>
        public T Find<T>(object id) where T : class
        {
            return this.Context.Set<T>().Find(id);
        }

        /// <summary>
        /// 不应该暴露给上端使用者，尽量少用
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        [Obsolete("尽量避免使用，using 带表达式目录树的代替")]
        public IQueryable<T> Set<T>() where T : class
        {
            return this.Context.Set<T>();
        }

        /// <summary>
        /// 这才是合理的做法，上端给条件，这里查询
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="funcWhere"></param>
        /// <returns></returns>
        public IQueryable<T> Query<T>(Expression<Func<T, bool>> funcWhere) where T : class
        {
            return this.Context.Set<T>().Where<T>(funcWhere);
        }

        /// <summary>
        /// 分页查询
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="S"></typeparam>
        /// <param name="funcWhere">查询条件表达式目录树</param>
        /// <param name="pageSize">页大小</param>
        /// <param name="pageIndex">页索引</param>
        /// <param name="funcOrderby">按什么字段排序</param>
        /// <param name="isAsc">升序还是降序</param>
        /// <returns></returns>
        public PageResult<T> QueryPage<T, S>(Expression<Func<T, bool>> funcWhere, int pageSize, int pageIndex, Expression<Func<T, S>> funcOrderby, bool isAsc = true) where T : class
        {
            var list = this.Set<T>();
            if (funcWhere != null)
            {
                list = list.Where<T>(funcWhere);
            }
            if (isAsc)
            {
                list = list.OrderBy(funcOrderby);
            }
            else
            {
                list = list.OrderByDescending(funcOrderby);
            }
            PageResult<T> result = new PageResult<T>()
            {
                DataList = list.Skip((pageIndex - ) * pageSize).Take(pageSize).ToList(),
                PageIndex = pageIndex,
                PageSize = pageSize,
                TotalCount = this.Context.Set<T>().Count(funcWhere)
            };
            return result;
        }
        #endregion

        #region Insert
        /// <summary>
        /// 插入
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        /// <returns></returns>
        public T Insert<T>(T t) where T : class
        {
            this.Context.Set<T>().Add(t);
            return t;
        }

        /// <summary>
        /// 插入集合
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="tList"></param>
        /// <returns></returns>
        public IEnumerable<T> Insert<T>(IEnumerable<T> tList) where T : class
        {
            this.Context.Set<T>().AddRange(tList);
            return tList;
        }
        #endregion

        #region Update
        /// <summary>
        /// 是没有实现查询，直接更新的,需要Attach和State
        ///
        /// 如果是已经在context，只能再封装一个(在具体的service)
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        public void Update<T>(T t) where T : class
        {
            if (t == null) throw new Exception("t is null");

            this.Context.Set<T>().Attach(t);//将数据附加到上下文，支持实体修改和新实体，重置为UnChanged
            this.Context.Entry<T>(t).State = EntityState.Modified;//全字段更新
        }

        /// <summary>
        /// 集合修改
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="tList"></param>
        public void Update<T>(IEnumerable<T> tList) where T : class
        {
            foreach (var t in tList)
            {
                this.Context.Set<T>().Attach(t);
                this.Context.Entry<T>(t).State = EntityState.Modified;
            }
        }

        /// <summary>
        /// 更新数据，指定更新哪些列，哪怕有些列值发生了变化，没有指定列也不能修改
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        public void UpdateSpecifyFiled<T>(T t, List<string> filedList) where T : class
        {
            this.Context.Set<T>().Attach(t);//将数据附加到上下文
            foreach(var filed in filedList)
            {
                this.Context.Entry<T>(t).Property(filed).IsModified = true;//指定某字段被改过
            }
        }
        #endregion

        #region Delete
        /// <summary>
        /// 先附加 再删除
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="t"></param>
        public void Delete<T>(T t) where T : class
        {
            if (t == null) throw new Exception("t is null");
            this.Context.Set<T>().Attach(t);
            this.Context.Set<T>().Remove(t);
        }

        /// <summary>
        /// 还可以增加非即时commit版本的，
        /// 做成protected
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="Id"></param>
        public void Delete<T>(int Id) where T : class
        {
            T t = this.Find<T>(Id);//也可以附加
            if (t == null) throw new Exception("t is null");
            this.Context.Set<T>().Remove(t);
        }

        /// <summary>
        /// 删除集合
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="tList"></param>
        public void Delete<T>(IEnumerable<T> tList) where T : class
        {
            foreach (var t in tList)
            {
                this.Context.Set<T>().Attach(t);
            }
            this.Context.Set<T>().RemoveRange(tList);
        }
        #endregion

        #region Other
        /// <summary>
        /// 一次性提交
        /// </summary>
        public void Commit()
        {
            this.Context.SaveChanges();
        }

        /// <summary>
        /// sql语句查询
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public IQueryable<T> ExcuteQuery<T>(string sql, SqlParameter[] parameters) where T : class
        {
            return this.Context.Database.SqlQuery<T>(sql, parameters).AsQueryable();
        }

        /// <summary>
        /// 执行sql语句
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        public void Excute<T>(string sql, SqlParameter[] parameters) where T : class
        {
            DbContextTransaction trans = null;
            try
            {
                trans = this.Context.Database.BeginTransaction();
                this.Context.Database.ExecuteSqlCommand(sql, parameters);
                trans.Commit();
            }
            catch (Exception ex)
            {
                if (trans != null)
                    trans.Rollback();
                throw ex;
            }
        }

        public virtual void Dispose()
        {
            if (this.Context != null)
            {
                this.Context.Dispose();
            }
        }
        #endregion
    }
}

• 整合Unity，实现IOC，依赖注入解决问题

虽然封装完了，但是还是带来了2个问题，问题如下代码所示，所以我们需要解决下面两个问题
问题1：通过封装，完成了通过Service来完成对数据库的访问，但是右边 new StudentService()是细节，不满足依赖倒置原则，应该面向抽象编程
问题2：构造new StudentService()的时候需要一个Context，不能每次都SchoolDBEntities dbContext = new SchoolDBEntities();

{
    SchoolDBEntities dbContext = new SchoolDBEntities();
    using (IStudentService iStudentService = new StudentService(dbContext))
    {
        Student student = iStudentService.Find<Student>("");

        Student student1 = new Student();
        student1.Student_ID = "";
        student1.Student_Name = "Student1";
        iStudentService.Insert(student1);

        iStudentService.Commit();
    }
}

1、Nuget引入Unity相关dll

2、配置Unity.Config

.2.1、给BaseService注入DbContext

<register type="System.Data.Entity.DbContext, EntityFramework" mapTo="David.General.EF.Model.SchoolDBEntities,David.General.EF.Model"/>

type中逗号前是完整类型名称，也就是命名空间System.Data.Entity+类名DbContext，逗号后是dll名称EntityFramework

mapTo中逗号前是完整类型名称，也就是命名空间David.General.EF.Model+类名SchoolDBEntities，逗号后是dll名称David.General.EF.Model

2.2、给IStudentService注入StudentService

<register type="David.General.EF.Bussiness.Interface.IStudentService,David.General.EF.Bussiness.Interface" mapTo="David.General.EF.Bussiness.Service.StudentService, David.General.EF.Bussiness.Service">

type中逗号前是完整类型名称，也就是命名空间David.General.EF.Bussiness.Interface+接口名IStudentService，逗号后是dll名称David.General.EF.Bussiness.Interface

mapTo中逗号前是完整类型名称，也就是命名空间David.General.EF.Bussiness.Service+类名StudentService，逗号后是dll名称David.General.EF.Bussiness.Service

<configuration>
  <configSections>
    <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Unity.Configuration"/>
  </configSections>
  <unity>
    <sectionExtension type="Microsoft.Practices.Unity.InterceptionExtension.Configuration.InterceptionConfigurationExtension, Unity.Interception.Configuration"/>
    <containers>
      <container name="MyContainer">
        <extension type="Interception"/>
        <register type="System.Data.Entity.DbContext, EntityFramework" mapTo="David.General.EF.Model.SchoolDBEntities,David.General.EF.Model"/>
        <register type="David.General.EF.Bussiness.Interface.IStudentService,David.General.EF.Bussiness.Interface" mapTo="David.General.EF.Bussiness.Service.StudentService, David.General.EF.Bussiness.Service">
        </register>
      </container>
    </containers>
  </unity>
</configuration>

3、调用服务
如下调用代码和截图所示
首先：我们构建学生服务的时候，没有出现细节StudentService
其次：在构建学生服务的时候，没有显式的去传入DbContext，StudentService继承BaseService，StudentService的构造函数的参数DbContext是来源于BaseService，而BaseService依赖的DbContext是通过构造函数注入进来的

{
　　//UnityConfig配置只用初始化一次，所以我们把读取UnityConfig配置封装一下
　　//使用单例模式，l利用静态构造函数只初始化1次的特点，达到配置只初始化1次
　　Unity.IUnityContainer container = ContainerFactory.GetContainer();

　　//IOC：去掉细节依赖，降低耦合，增强扩展性
　　using (IStudentService iStudentService = container.Resolve<IStudentService>())
　　{
　　　　Student student = iStudentService.Find<Student>("");

　　　　//测试指定更新
　　　　Student oldStudent = new Student()
　　　　{
　　　　　　Student_ID = "",
　　　　　　Student_Name = "猪猪",
　　　　　　Student_Sex = "男"
　　　　};

　　　　List<string> filedList = new List<string>();
　　　　filedList.Add("Student_Name");
　　　　iStudentService.UpdateSpecifyFiled<Student>(oldStudent, filedList);
　　　　iStudentService.Commit();
　　}
}

namespace David.General.EF.Bussiness.Service
{
    public class StudentService : BaseService,IStudentService
    {
        public StudentService(DbContext context) : base(context)
        {
        }

        /// <summary>
        /// 记录学生打架
        /// </summary>
        /// <param name="student"></param>
        public void RecordStudentFight(Student student)
        {
            base.Insert(student);
            this.Commit();
        }
    }
}