前言

之前我们系统学习了EntityFramework，个人觉得有些东西不能学了就算完了，必须要学以致用，在Web API上也少不了增（C）、删（D）、改（U）、查（R）。鉴于此，我们通过EF来实现Web API上的增删改查。

之前对于EF的基本操作都是很零散的，我们应该对于CRUD都是通过完整封装来实现，并且也显得比较专业，接下来首先对EF利用Responsitory仓储模式进行完整封装。

EntityFramework完整封装

我们建立一个Core（核心类库），里面存放有关EF的完成封装。

第一步

建立所有实体的基类，将实体的公共属性放入其中，取为BaseEntity

    public class BaseEntity<T>
    {
        public T Id { get; set; }
    }

第二步

建立仓储接口IRepository，包括基本的增、删、改、查等方法

    public interface IRepository<TEntity> where TEntity : class
    {
        /// <summary>
        /// 获得数据列表
        /// </summary>
        /// <returns></returns>
        IQueryable<TEntity> GetList();

        /// <summary>
        /// 通过id获得实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        TEntity GetById(object id);

        /// <summary>
        /// 添加实体
        /// </summary>
        /// <param name="entity"></param>
        int Insert(TEntity entity);


        /// <summary>
        /// 添加实体集合
        /// </summary>
        /// <param name="entities"></param>
        int Insert(IEnumerable<TEntity> entities);

        /// <summary>
        /// 删除实体
        /// </summary>
        /// <param name="entity"></param>
        int Delete(TEntity entity);


        /// <summary>
        /// 根据条件删除实体
        /// </summary>
        /// <param name="entities"></param>
        int DeleteByRequirement(Expression<Func<TEntity, bool>> func);


        /// <summary>
        /// 更新实体
        /// </summary>
        /// <param name="entity"></param>
        int Update(TEntity entity);



        /// <summary>
        /// 更新实体集合
        /// </summary>
        /// <param name="entities"></param>
        int Update(IEnumerable<TEntity> entities);

    }

第三步

利用仓储服务RepositoryService实现上述仓储接口IRepository

    public class RepositoryService<TEntity> : IRepository<TEntity> where TEntity : class
    {
        private IDbContext Context;
        private bool IsNoTracking;

        /// <summary>
        /// 获取实体集合
        /// </summary>
        private IDbSet<TEntity> Entities
        {
            get
            {

                return this.Context.Set<TEntity>();
            }
        }

        private DbEntityEntry Entry(TEntity entity)
        {
            return this.Context.Entry<TEntity>(entity);
        }

        public RepositoryService(IDbContext context, bool isNoTracking)
        {

            this.Context = context;
            this.IsNoTracking = isNoTracking;
        }

        /// <summary>
        /// 获取所有数据
        /// </summary>
        /// <returns></returns>
        public IQueryable<TEntity> GetList()
        {
            if (!IsNoTracking)
                return this.Entities.AsQueryable();
            else
                return this.Entities.AsNoTracking().AsQueryable();
        }

        /// <summary>
        /// 通过id获取实体
        /// </summary>
        /// <param name="id"></param>
        /// <returns></returns>
        public TEntity GetById(object id)
        {
            return Entities.Find(id);

        }

        /// <summary>
        /// 添加实体
        /// </summary>
        /// <param name="entity"></param>
        public int Insert(TEntity entity)
        {
            Entities.Add(entity);
            return this.Context.SaveChanges();
        }

        public int Insert(IEnumerable<TEntity> entities)
        {
            if (entities == null)
                throw new ArgumentNullException("entities");
            foreach (var entity in entities)
            {
                Entities.Add(entity);
            }
            return this.Context.SaveChanges();
        }

        /// <summary>
        /// 删除实体
        /// </summary>
        /// <param name="entity"></param>
        public int Delete(TEntity entity)
        {
            if (!IsNoTracking)
                this.Entities.Remove(entity);
            else
                this.Entities.Attach(entity);
            this.Entities.Remove(entity);
            return this.Context.SaveChanges();
        }

        public int DeleteByRequirement(Expression<Func<TEntity, bool>> func)
        {
            var list = GetList().Where(func).ToList();
            list.ForEach(e =>
            {
                if (!IsNoTracking)
                    this.Entities.Remove(e);
                else
                    this.Entities.Attach(e);
                this.Entities.Remove(e);
            });

            return this.Context.SaveChanges();
        }

        /// <summary>
        /// 更新实体
        /// </summary>
        /// <param name="entity"></param>
        public int Update(TEntity entity)
        {
            if (!IsNoTracking)
                return this.Context.SaveChanges();
            else
                this.Context.Entry(entity).State = EntityState.Modified;
            return this.Context.SaveChanges();
        }

        public int Update(IEnumerable<TEntity> entities)
        {
            if (entities == null)
                throw new ArgumentNullException("enetities");
            if (!IsNoTracking)
                return this.Context.SaveChanges();
            else
                foreach (var t in entities)
                {
                    this.Context.Entry(t).State = EntityState.Modified;
                }

            return this.Context.SaveChanges();
        }


        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                if (Context != null)
                {
                    this.Context.Dispose();
                    this.Context = null;
                }
            }
        }

    }

第四步

用接口IDbContext封装EF上下文DbContext中的公共方法

    public interface IDbContext
    {

        /// <summary>
        /// 获得实体集合
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <returns></returns>
        IDbSet<TEntity> Set<TEntity>() where TEntity : class;


        /// <summary>
        /// 执行存储过程
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="commandText"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        IList<TEntity> ExecuteStoredProcedureList<TEntity>(string commandText, params object[] parameters)
        where TEntity : class;


        /// <summary>
        /// 执行SQL语句查询
        /// </summary>
        /// <typeparam name="TElement"></typeparam>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        IEnumerable<TElement> SqlQuery<TElement>(string sql, params object[] parameters);


        DbEntityEntry Entry<TEntity>(TEntity entity) where TEntity : class;

        /// <summary>
        /// 保存数据
        /// </summary>
        /// <returns></returns>
        int SaveChanges();

       

        /// <summary>
        /// 变更追踪代码
        /// </summary>
        bool ProxyCreationEnabled { get; set; }


        /// <summary>
        /// DetectChanges方法自动调用
        /// </summary>
        bool AutoDetectChangesEnabled { get; set; }

        /// <summary>
        /// 调用Dispose方法
        /// </summary>
        void Dispose();

    }

第五步

实现EF上下文中的数据库连接、模型初始化以及映射等（也可以手动关闭全局变更追踪相对比较灵活）

    public class EFDbContext : DbContext, IDbContext
    {
        public EFDbContext(string connectionString)
            : base(connectionString)
        { }


        static EFDbContext()
        {
            Database.SetInitializer<EFDbContext>(new DropCreateDatabaseIfModelChanges<EFDbContext>());
        }

        /// <summary>
        /// 一次性加载所有映射
        /// </summary>
        /// <param name="modelBuilder"></param>
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {

            var typesToRegister = Assembly.GetExecutingAssembly().GetTypes()
            .Where(type => !String.IsNullOrEmpty(type.Namespace))
            .Where(type => type.BaseType != null && type.BaseType.IsGenericType &&
                type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
            foreach (var type in typesToRegister)
            {
                dynamic configurationInstance = Activator.CreateInstance(type);
                modelBuilder.Configurations.Add(configurationInstance);
            }


            base.OnModelCreating(modelBuilder);
        }

        /// <summary>
        /// 获得实体集合
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <returns></returns>
        public new IDbSet<TEntity> Set<TEntity>() where TEntity : class
        {
            return base.Set<TEntity>();

        }

        /// <summary>
        /// 实体状态
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="entity"></param>
        /// <returns></returns>

        public new DbEntityEntry Entry<TEntity>(TEntity entity) where TEntity : class
        {
            return base.Entry<TEntity>(entity);
        }

        /// <summary>
        /// 执行存储过程
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="commandText"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public IList<TEntity> ExecuteStoredProcedureList<TEntity>(string commandText, params object[] parameters) where TEntity : class
        {

            if (parameters != null && parameters.Length > 0)
            {
                for (int i = 0; i <= parameters.Length - 1; i++)
                {
                    var p = parameters[i] as DbParameter;
                    if (p == null)
                        throw new Exception("Not support parameter type");

                    commandText += i == 0 ? " " : ", ";

                    commandText += "@" + p.ParameterName;
                    if (p.Direction == ParameterDirection.InputOutput || p.Direction == ParameterDirection.Output)
                    {

                        commandText += " output";
                    }
                }
            }

            var result = this.Database.SqlQuery<TEntity>(commandText, parameters).ToList();


            bool acd = this.Configuration.AutoDetectChangesEnabled;
            try
            {
                this.Configuration.AutoDetectChangesEnabled = false;

                for (int i = 0; i < result.Count; i++)
                    result[i] = this.Set<TEntity>().Attach(result[i]);
            }
            finally
            {
                this.Configuration.AutoDetectChangesEnabled = acd;
            }

            return result;
        }


        /// <summary>
        /// SQL语句查询
        /// </summary>
        /// <typeparam name="TElement"></typeparam>
        /// <param name="sql"></param>
        /// <param name="parameters"></param>
        /// <returns></returns>
        public IEnumerable<TElement> SqlQuery<TElement>(string sql, params object[] parameters)
        {
            return this.Database.SqlQuery<TElement>(sql, parameters);
        }


        /// <summary>
        /// 当查询或者获取值时是否启动创建代理
        /// </summary>
        public virtual bool ProxyCreationEnabled
        {
            get
            {
                return this.Configuration.ProxyCreationEnabled;
            }
            set
            {
                this.Configuration.ProxyCreationEnabled = value;
            }
        }


        /// <summary>
        /// 当查询或者获取值时指定是否开启自动调用DetectChanges方法
        /// </summary>
        public virtual bool AutoDetectChangesEnabled
        {
            get
            {
                return this.Configuration.AutoDetectChangesEnabled;
            }
            set
            {
                this.Configuration.AutoDetectChangesEnabled = value;
            }
        }

    }

以上就是对利用EntityFramework来实现基本操作的完整封装。接下来就是相关类以及映射（场景：一个Student对应一个Flower，而一个Flower对应多个Student）

Student

    public class Student : BaseEntity<int>
    {

        public string Name { get; set; }


        public int FlowerId { get; set; }
        public virtual Flower Flower { get; set; }
    }

Flower

   public class Flower : BaseEntity<int>
    {

        public string Remark { get; set; }

        public virtual ICollection<Student> Students { get; set; }
    }

CRUD

接下来就是Web API控制器中执行增、删等操作，我们创建一个StudentController控制器，然后首先创建仓储服务。（执行Action方法，依据默认约定，未添加特性）

        public IRepository<Student> _repository;
        public EFDbContext _ctx;
        public StudentController()
        {
            _ctx = new EFDbContext("DBByConnectionString");
            _repository = new RepositoryService<Student>(_ctx, true);  //关闭局部变更追踪
        }

执行R操作（即默认请求到HttpGet方法）

        public IEnumerable<Student> GetAllStudent()
        {

            return _repository.GetList().Select(d => new Student { Name = d.Name, Flower = d.Flower, Id = d.Id }).ToList();

        }

当执行此查询操作时却出错了，真遗憾：

上述修改如下即可：

 return _repository.GetList().ToList().Select(d => new Student { Name = d.Name, Flower = d.Flower, Id = d.Id }).ToList();

不知道还有没有更好的解决方案，用ToList直接将所有数据进行加载到内存中，在性能上消耗比较大。（期待你的解决方案）

特此记录

在此感谢园友（_天光云影）给出的解决方案，在GetList之后利用 Linq 进行Select，最后进行ToList即可！！！

执行CUD等操作

 
  
 View Code 

总结

这节主要介绍了利用仓储模式完整封装EF来进行Web API基本操作，基本操作中关于返回状态码等信息，无非就是以下几个对象

HttpResponseException  返回异常

HttpResponseMessage   返回信息（诸如状态码等）

HttpStatusCode       状态码枚举（如页面未找到等）

本文转自Jeffcky博客园博客，原文链接：http://www.cnblogs.com/CreateMyself/p/4820121.html，如需转载请自行联系原作者

Web APi之EntityFramework【CRUD】（三）

前言