分享基于EF6、Unitwork、Autofac的Repository模式设计

一、实现的思路和结构图

• Repository的共同性

有一些公共的方法(增删改查)， 这些方法无关于Repository操作的是哪个实体类，可以把这些方法定义成接口IRepository，然后有个基类BaseRepository实现该接口的方法。常见的方法，比如Find, Filter, Delete, Create等

• Repository的差异性

每个Repository类又会有一些差异性，应当允许它们能够继承BaseRepository之外，还能够再扩展自己的一些方法。所以每个类都可以再定义一个自己特有的接口，定义一些属于自己Repository的方法。

• Repository的协同性

  不同的Repository可能需要协同，Repository对数据的修改，需要在统一的保存.
  最终实现的类结构图如下:

二、Repository设计具体的实现代码

IRepository接口定义了Repository共有的方法, BaseRepository实现了这些接口的方法。其它的Repository类再集成BaseRepository方法，就天然的得到了对数据操作的基本方法。

• IRepository代码

    public interface IRepository<TEntity> where TEntity : class{/// <summary>/// Gets all objects from database/// </summary>/// <returns></returns>IQueryable<TEntity> All();/// <summary>/// Gets objects from database by filter./// </summary>/// <param name="predicate">Specified a filter</param>/// <returns></returns>IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> predicate);/// <summary>/// Gets objects from database with filtering and paging./// </summary>/// <param name="filter">Specified a filter</param>/// <param name="total">Returns the total records count of the filter.</param>/// <param name="index">Specified the page index.</param>/// <param name="size">Specified the page size</param>/// <returns></returns>IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> filter, out int total, int index = 0, int size = 50);/// <summary>/// Gets the object(s) is exists in database by specified filter./// </summary>/// <param name="predicate">Specified the filter expression</param>/// <returns></returns>bool Contains(Expression<Func<TEntity, bool>> predicate);/// <summary>/// Find object by keys./// </summary>/// <param name="keys">Specified the search keys.</param>/// <returns></returns>TEntity Find(params object[] keys);/// <summary>/// Find object by specified expression./// </summary>/// <param name="predicate"></param>/// <returns></returns>TEntity Find(Expression<Func<TEntity, bool>> predicate);/// <summary>/// Create a new object to database./// </summary>/// <param name="t">Specified a new object to create.</param>/// <returns></returns>void Create(TEntity t);/// <summary>/// Delete the object from database./// </summary>/// <param name="t">Specified a existing object to delete.</param>void Delete(TEntity t);/// <summary>/// Delete objects from database by specified filter expression./// </summary>/// <param name="predicate"></param>/// <returns></returns>int Delete(Expression<Func<TEntity, bool>> predicate);/// <summary>/// Update object changes and save to database./// </summary>/// <param name="t">Specified the object to save.</param>/// <returns></returns>void Update(TEntity t);/// <summary>/// Select Single Item by specified expression./// </summary>/// <param name="expression"></param>/// <returns></returns>TEntity FirstOrDefault(Expression<Func<TEntity, bool>> expression);}

• BaseRepository代码

    public class BaseRepository<TEntity> : IRepository<TEntity> where TEntity : class{protected readonly DbContext Context;public BaseRepository(DbContext context){Context = context;}/// <summary>/// Gets all objects from database/// </summary>/// <returns></returns>public IQueryable<TEntity> All(){return Context.Set<TEntity>().AsQueryable();}/// <summary>/// Gets objects from database by filter./// </summary>/// <param name="predicate">Specified a filter</param>/// <returns></returns>public virtual IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> predicate){return Context.Set<TEntity>().Where<TEntity>(predicate).AsQueryable<TEntity>();}/// <summary>/// Gets objects from database with filtering and paging./// </summary>/// <param name="filter">Specified a filter</param>/// <param name="total">Returns the total records count of the filter.</param>/// <param name="index">Specified the page index.</param>/// <param name="size">Specified the page size</param>/// <returns></returns>public virtual IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> filter, out int total, int index = 0,int size = 50){var skipCount = index * size;var resetSet = filter != null? Context.Set<TEntity>().Where<TEntity>(filter).AsQueryable(): Context.Set<TEntity>().AsQueryable();resetSet = skipCount == 0 ? resetSet.Take(size) : resetSet.Skip(skipCount).Take(size);total = resetSet.Count();return resetSet.AsQueryable();}/// <summary>/// Gets the object(s) is exists in database by specified filter./// </summary>/// <param name="predicate">Specified the filter expression</param>/// <returns></returns>public bool Contains(Expression<Func<TEntity, bool>> predicate){return Context.Set<TEntity>().Any(predicate);}/// <summary>/// Find object by keys./// </summary>/// <param name="keys">Specified the search keys.</param>/// <returns></returns>public virtual TEntity Find(params object[] keys){return Context.Set<TEntity>().Find(keys);}/// <summary>/// Find object by specified expression./// </summary>/// <param name="predicate"></param>/// <returns></returns>public virtual TEntity Find(Expression<Func<TEntity, bool>> predicate){return Context.Set<TEntity>().FirstOrDefault<TEntity>(predicate);}/// <summary>/// Create a new object to database./// </summary>/// <param name="t">Specified a new object to create.</param>/// <returns></returns>public virtual void Create(TEntity t){Context.Set<TEntity>().Add(t);}/// <summary>/// Delete the object from database./// </summary>/// <param name="t">Specified a existing object to delete.</param>public virtual void Delete(TEntity t){Context.Set<TEntity>().Remove(t);}/// <summary>/// Delete objects from database by specified filter expression./// </summary>/// <param name="predicate"></param>/// <returns></returns>public virtual int Delete(Expression<Func<TEntity, bool>> predicate){var objects = Filter(predicate);foreach (var obj in objects)Context.Set<TEntity>().Remove(obj);return Context.SaveChanges();}/// <summary>/// Update object changes and save to database./// </summary>/// <param name="t">Specified the object to save.</param>/// <returns></returns>public virtual void Update(TEntity t){try{var entry = Context.Entry(t);Context.Set<TEntity>().Attach(t);entry.State = EntityState.Modified;}catch (OptimisticConcurrencyException ex){throw ex;}}/// <summary>/// Select Single Item by specified expression./// </summary>/// <param name="expression"></param>/// <returns></returns>public TEntity FirstOrDefault(Expression<Func<TEntity, bool>> expression){return All().FirstOrDefault(expression);}}

IUnitOfWork接口定义了方法获取特定的Repository, 执行存储过程, SaveChange方法提交修改，统一更新数据。

• IUnitOfWork接口代码:

    public interface IUnitOfWork : IDisposable{DbContext DbContext { get; }TRepository GetRepository<TRepository>() where TRepository : class;void ExecuteProcedure(string procedureCommand, params object[] sqlParams);void ExecuteSql(string sql);List<T> SqlQuery<T>(string sql);void SaveChanges();}

UnitOfWork代码, 代码中使用到了Autofac中的IComponentContext来获取Repository实例

    public class UnitOfWork : IUnitOfWork{private readonly IComponentContext _componentContext;protected readonly DbContext Context;public UnitOfWork(DbContext context, IComponentContext componentContext){Context = context;_componentContext = componentContext;}public DbContext DbContext => Context;public TRepository GetRepository<TRepository>() where TRepository : class{return _componentContext.Resolve<TRepository>();}public void ExecuteProcedure(string procedureCommand, params object[] sqlParams){Context.Database.ExecuteSqlCommand(procedureCommand, sqlParams);}public void ExecuteSql(string sql){Context.Database.ExecuteSqlCommand(sql);}public List<T> SqlQuery<T>(string sql){return Context.Database.SqlQuery<T>(sql).ToList();}public void SaveChanges(){try{Context.SaveChanges();}catch (InvalidOperationException ex){if (!ex.Message.Contains("The changes to the database were committed successfully")){throw;}}}public void Dispose(){Context?.Dispose();}}

三、Repository设计的具体的使用

这里我们定义一个IStudentRepository接口, 包含了方法GetAllStudents(), 同时继承于IRepository<Student>接口

public interface IStudentRepository : IRepository<Student>
{IEnumerable<dynamic> GetAllStudents();
}

接着定义StudentRepository类来实现这个接口

public class StudentRepository : BaseRepository<Student>, IStudentRepository
{private readonly SchoolContext _context;public StudentRepository(SchoolContext context): base(context){_context = context;}public IEnumerable<dynamic> GetAllStudents(){return _context.Students;}
}

• 在Application_Start方法中使用Autofac注册Repository的代码如下：

    var builder = new ContainerBuilder();//register controllersbuilder.RegisterControllers(typeof(MvcApplication).Assembly);//register repositorybuilder.RegisterAssemblyTypes(Assembly.GetExecutingAssembly()).AsImplementedInterfaces();//add the Entity Framework context to make sure only one context per requestbuilder.RegisterType<SchoolContext>().InstancePerRequest();builder.Register(c => c.Resolve<SchoolContext>()).As<DbContext>().InstancePerRequest();var container = builder.Build();DependencyResolver.SetResolver(new AutofacDependencyResolver(container));

• 在控制器中注入使用Repository的代码如下:

private readonly IUnitOfWork _repositoryCenter;private readonly IStudentRepository _studentRepository;public HomeController(IUnitOfWork repositoryCenter)
{_repositoryCenter = repositoryCenter;_studentRepository = _repositoryCenter.GetRepository<IStudentRepository>();
}public ActionResult Index(Student sessionStudent)
{var students = _studentRepository.GetAllStudents();// 同时你也可以使用定义于IRepository<Student>中的方法， 比如:_studentRepository.Delete(students.First());_repositoryCenter.SaveChanges();...return View(students);
}

四、思路总结

上面的设计，把Repository的通用代码剥离到父类中，同时又允许每个Repository扩展自己的方法，达到了比较理想的状态。

只是现在的设计和Autofac耦合了，但是如果想继续剥离Autofac直接使用 _repositoryCenter.GetRepository<IStudentRepository>(); 的方式获取IStudentRepository的实例就很困难了。

五、案例源码

源代码仓库 AutoFacMvc