基于Repository模式设计项目架构—你可以参考的项目架构设计

关于Repository模式，直接百度查就可以了，其来源是《企业应用架构模式》。
我们新建一个Infrastructure文件夹，这里就是基础设施部分，EF Core的上下文类以及Repository层都放在这里面。
新建一个IReposotory的接口，其内容就是封装了基本的CRUD:

public interface IRepository<TEntity> where TEntity : class
 {
    ///获取当前实体的查询数据集
    IQueryable<TEntity> Entities{get;} 

    ///获取当前实体的数据集
    DbSet<TEntity> DbEntities{get;} 

 /// <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 filting 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 = , int size = ); 

 /// <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>
 int 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>
 int Update(TEntity t); 

 /// <summary>
 /// Select Single Item by specified expression.
 /// </summary>
 /// <typeparam name="T"></typeparam>
 /// <param name="expression"></param>
 /// <returns></returns>
 TEntity FirstOrDefault(Expression<Func<TEntity, bool>> expression);
 }

创建一个基类，用来实现IRepository接口，同时作其余的Repository的基类

public class BaseRepository<TEntity> : IRepository<TEntity> where TEntity : class
 {
 protected readonly DbContext Context; 

 public BaseRepository(DbContext context)
 {
 Context = context;
 } 

/// 获取当前实体的查询数据集
public IQueryable<TEntity> Entities
{
get { return Context.Set<TEntity>().AsQueryable(); }
} 

/// 获取当前实体
public IQueryable<TEntity> Entities
{
get { return Context.Set<TEntity>(); }
} 

 public TEntity FirstOrDefault(Expression<Func<TEntity, bool>> expression)
 {
 return All().FirstOrDefault(expression);
 } 

 public IQueryable<TEntity> All()
 {
 return Context.Set<TEntity>().AsQueryable();
 } 

 public virtual IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> predicate)
 {
 return Context.Set<TEntity>().Where<TEntity>(predicate).AsQueryable<TEntity>();
 } 

 public virtual IQueryable<TEntity> Filter(Expression<Func<TEntity, bool>> filter, out int total, int index = ,
 int size = )
 {
 var skipCount = index * size;
 var resetSet = filter != null
 ? Context.Set<TEntity>().Where<TEntity>(filter).AsQueryable()
 : Context.Set<TEntity>().AsQueryable();
 resetSet = skipCount ==  ? resetSet.Take(size) : resetSet.Skip(skipCount).Take(size);
 total = resetSet.Count();
 return resetSet.AsQueryable();
 } 

 public virtual int Create(TEntity TObject)
 {
 Entities.Add(TObject);
 Context.SaveChanges();
 } 

 public virtual int Delete(TEntity TObject)
 {
 Entities.Remove(TObject);.
 Context.SaveChanges();
 } 

 public virtual void Update(TEntity TObject)
 {
 try
 {
 var entry = Context.Entry(TObject);
 Context.Set<TEntity>().Attach(TObject);
 entry.State = EntityState.Modified;
 }
 catch (OptimisticConcurrencyException ex)
 {
 throw ex;
 }
 } 

 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();
 } 

 public bool Contains(Expression<Func<TEntity, bool>> predicate)
 {
 return Context.Set<TEntity>().Any(predicate);
 } 

 public virtual TEntity Find(params object[] keys)
 {
 return Context.Set<TEntity>().Find(keys);
 } 

 public virtual TEntity Find(Expression<Func<TEntity, bool>> predicate)
 {
 return Context.Set<TEntity>().FirstOrDefault<TEntity>(predicate);
 }
 }

新建一个实体类的接口：

public interface IStudentRepository : IRepository<Student>
 {
 int AddStudent(Student student);
 }

然后我们创建一个实体类的Repository：

public class StudentRepository : BaseRepository<Student>, IStudentRepository
 {
 private readonly SchoolContext _context; 

 public StudentRepository(SchoolContext context)
 : base(context)
 {
 _context = context;
 } 

int AddStudent(Student student)
{
_context.Create(student);
}
 }

在这里就已经做好了我们要做的了。接下来的就是注入依赖、在控制器里面的使用了。

我们完全可以自己来定制自己的Repository模式下的项目。其实整个的架构没有什么，我们只是将所有的CRUD操作封装到了IRepository接口里面，然后在BaseRepository中实现了一遍，而且如果你细心的话，你会发现IRepository里面的CRUD操作都是基于已有的扩展方法里面的，就是linq扩展方法的Add等源码，同时我们在BaseRepository类中，提供了DbSet<TEntity>属性以及查询数据集IQueryable<DbSet<TEntity>>，这也是有必要的，可以省却我们很多不必要的代码，因为我们所有的CRUD都是基于这两个的。然后我们基于BaseRepository来实现实体类的Repository，同时继承按需增加的IEntityRepository接口。但是在这里要注意，我们将DbContext的子类都放在了Infrastructure文件夹里面，是因为，一般我们继承自DbContext的子类都是操作数据库的中间类，属于基础设施一块，所以将其放在Infrastructure文件夹比较合适。

参考资料：
MVC实用架构设计（三）——EF-Code First（1）：Repository，UnitOfWork，DbContext

分享基于Entity Framework的Repository模式设计（附源码）

《ASP.NET MVC框架揭秘》源码中的示例项目源码 S1402