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; } }
相关映射
public class StudentMap:EntityTypeConfiguration<Student> { public StudentMap() { ToTable("Student"); HasKey(p => p.Id); Property(p => p.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); HasRequired(p => p.Flower).WithMany(p => p.Students).HasForeignKey(p => p.FlowerId); } } public class FlowerMap:EntityTypeConfiguration<Flower> { public FlowerMap() { ToTable("Flower"); HasKey(p => p.Id); Property(p => p.Id).HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity); } }
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
public Student GetStudentById(int id) { var student = _repository.GetById(id); if (student == null) throw new HttpResponseException(HttpStatusCode.NotFound); else return student; } //添加操作（HttpPost） public HttpResponseMessage PostStudent(Student stu) { var insertStudent = _repository.Insert(stu); var response = Request.CreateResponse<Student>(HttpStatusCode.Created, stu); string uri = Url.Link("DefaultApi", new { id = stu.Id }); response.Headers.Location = new Uri(uri); return response; } //更新操作（HttpPut） public void PutStudent(int id, Student stu) { stu.Id = id; if (_repository.Update(stu) <= 0) { throw new HttpResponseException(HttpStatusCode.NotFound); } } //删除操作（HttpDelete） public void DeleteStudent(int id) { Student stu = _repository.GetById(id); if (stu == null) { throw new HttpResponseException(HttpStatusCode.NotFound); } _repository.Delete(stu); }
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）
源代码下载
