通用存储库/工作单元问题

Question

我一直在学习各种来源的知识库和工作单元模式,包括:

http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net- MVC应用程序

如果您浏览上面的thr链接到创建工作单元类,则有以下内容:

    private GenericRepository<Department> departmentRepository;
    private GenericRepository<Course> courseRepository;

这很好,但我想继续扩展Generic的工作单元类并设置GenericRepositories的集合,这样我就可以根据我通过的模型进行动态更新.

我最终想在我的控制器中执行以下操作:

public class LedgerUserController : Controller
{
    private GenericUnitOfWork unitOfWork = new GenericUnitOfWork();
    LedgerUser ledgeruser = new LedgerUser();


    public ActionResult Index()
    {
        //var ledgerusers = db.LedgerUsers.Include(l => l.Image).Include(l => l.UserType);
        var view = unitOfWork.Repository(ledgeruser).Get(l => l.LastName == "smith");
        return View(view.ToList());
    }
}

所以这是我的类和接口到目前为止:

IRepository.cs

/// <summary>
/// Generic Repository for CRUD Operations and methods
/// to locate entities within your store. This is not specific to which Data Access
/// tools your are using (Direct SQL, EF, NHibernate, etc).
/// </summary>
public interface IRepository<T> where T : class
{
    //--Search Operations
    IQueryable<T> GetAll();
    IEnumerable<T> GetAllList();
    IEnumerable<T> Get(Expression<Func<T,bool>> filter);
    T GetIt(Expression<Func<T, bool>> filter);
    T GetById(object id);


    //--CRUD Operations
    void Create(T entity);
    void Update(T entity);
    void Delete(T entity);

}

GenericRepository.cs

/// ///用于查找实体的存储库类/// CRUD操作/// ///公共类GenericRepository:IRepository其中TEntity:class {

    internal AccountsContext context;
    internal DbSet<TEntity> dbSet;
    internal IQueryable<TEntity> query;

    /// <summary>
    /// Default Constructor.
    /// </summary>
    /// <param name="context"></param>
    public GenericRepository(AccountsContext context)
    {
        this.context = context;
        this.dbSet = context.Set<TEntity>();
    }

    #region Methods
    #region Search Functionality
    /// <summary>
    /// Obtain the whole Entity to query if needed.
    /// </summary>
    /// <returns>IQueryable object.</returns>
    public virtual IQueryable<TEntity> GetAll()
    {
        IQueryable<TEntity> query = dbSet;
        return query;

    }

    /// <summary>
    /// Obtain the whole Entity to Enumerate throught if needed.
    /// </summary>
    /// <returns>IEnumerble object.</returns>
    public virtual IEnumerable<TEntity> GetAllList()
    {
        IQueryable<TEntity> query = dbSet;
        return query.ToList();

    }

    /// <summary>
    /// Locate an Entity by its indexed id.
    /// </summary>
    /// <param name="id"></param>
    /// <returns></returns>
    public virtual TEntity GetById(object id)
    {
        return dbSet.Find(id);
    }

    /// <summary>
    /// Gets a collection based on LINQ lambda expressions
    /// </summary>
    /// <param name="filter">Lambda Expression</param>
    /// <returns>Query</returns>
    public virtual IEnumerable<TEntity> Get(Expression<Func<TEntity, bool>> filter)
    {
        query = dbSet;

        if (filter != null)
        {
            query = query.Where(filter);
        }

        return this.query.ToList();
    }

    /// <summary>
    /// Gets one record based on a one-to-one relationship.
    /// </summary>
    /// <param name="filter">Lambda Expression.</param>
    /// <returns>One record.</returns>
    public virtual TEntity GetIt(Expression<Func<TEntity, bool>> filter)
    {
        IQueryable<TEntity> query = dbSet;
        return query.SingleOrDefault(filter);

    }


    #endregion
    #region CRUD Functionality

    /// <summary>
    /// Used to create a new entity into the database.
    /// </summary>
    /// <param name="entity">Entity to create.</param>
    public virtual void Create(TEntity entity)
    {
        dbSet.Add(entity);
    }

    /// <summary>
    /// Used to update an entity that already exists in the
    /// database.
    /// </summary>
    /// <param name="entity">Entity to update.</param>
    public virtual void Update(TEntity entity)
    {
        dbSet.Attach(entity);
        context.Entry(entity).State = EntityState.Modified;
    }

    /// <summary>
    /// Used to delete an entity from the database.
    /// </summary>
    /// <param name="entity">Entity to delete.</param>
    public virtual void Delete(TEntity entity)
    {
        if (context.Entry(entity).State == EntityState.Detached)
        {
            dbSet.Attach(entity);
        }
        dbSet.Remove(entity);
    }

    #endregion
    #endregion

}
#endregion

GenericUnitOfWork.cs:

  /// <summary>
/// Unit of work class that handles multiple Repositories
/// and shares the context.
/// </summary>
public class GenericUnitOfWork : IUnitOfWork

{
    private AccountsContext context = new AccountsContext();

    Dictionary<string, GenericRepository<IRepository<IRepositoryEntity>>> repostories = null;

    /// <summary>
    /// Generic Repository method which checks the repository is available if not,
    /// it sets it up.
    /// </summary>
    /// <param name="entity">Entity</param>
    /// <returns>Repository to use.</returns>
    public  GenericRepository<IRepository<IRepositoryEntity>> Repository (IRepositoryEntity entity)
    {

            string index = entity.GetType().ToString();

            if (!repostories.ContainsKey(index))
            {

                //Reflections to create the repoositiory if it is not needed.
                Type type1 = typeof(GenericRepository<>);
                Type[] typeArgs = {typeof(IRepositoryEntity)};

                Type constructed = type1.MakeGenericType(typeArgs);
                object o = Activator.CreateInstance(constructed);

                if(o is  GenericRepository<IRepository<IRepositoryEntity>>)
                {
                    var rep = (GenericRepository<IRepository<IRepositoryEntity>>)o;
                    rep.context = this.context;
                    repostories.Add(index, rep);  
                }

            }

            return this.repostories[index];
    }

    /// <summary>
    /// Save method.
    /// </summary>
    public void Save()
    {
        context.SaveChanges();

    }

    private bool disposed = false;

    /// <summary>
    /// Dispose the conxtext when finished.
    /// </summary>
    /// <param name="disposing"></param>
    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                context.Dispose();
            }
        }
        this.disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

}

}

现在我知道存储库Dictionary的实现和方法库不正确(通用类型是错误的)因为在我的lambda表达式中它无法解析ledgeruser LastName.

var view = unitOfWork.Repository(ledgeruser).Get(l => l.LastName == "smith");

我是在设计这个问题,还是有一个很好的干净方式来创建我的通用存储库集合,这些通用存储库是基于模型对象给出的(例如上面的LedgerUser)设置和创建的.

Answer 1

一些想法：

1. UnitOfWork您可以使用 IoC 容器并以这种方式自动创建存储库，而不是在实现中通过反射创建所有内容。MVC 框架实际上就是为这种方法构建的。有关为此目的使用 StructureMap 的简单说明和示例，请访问http://www.mikesdotnetting.com/Article/117/Dependency-Injection-and-Inversion-of-Control-with-ASP.NET-MVC。

2. 如果您不想使用成熟的 IoC 容器，您仍然可以根据接口标准化工厂逻辑和代码。这起到了同样的作用，但如果您想继续使用自定义工作单元实现，可能会效果更好。在我对C#/EF 和存储库模式的回答中：Where to put the ObjectContext in a Solution with multiple repositories? ，我发布了一个RepositoryProvider类，允许使用UnitOfWork可自定义工厂创建范围内的存储库。我建议至少查看此代码，因为它是实现代码示例目标的类似但更有效的方法。需要理解的一件重要的事情是，该答案中的示例使用 ObjectContext 作为 UnitOfWork，因此您的更改需要通过将出现的 替换为 的出现来解决这种ObjectContext差异IUnitOfWork。如果在检查代码后对该方法有任何不清楚的地方，请告诉我，我将尝试解释如何适应您的特定用例。

3. 您的工厂逻辑似乎存在一些循环。如果存储库创建了LedgerUsers，那么它不需要 aLedgerUser来创建工厂。在我看来，你真正想要的是Type像这样的参数unitOfWork.Repository(typeof(LedgerUser))。您可以通过在 load 上创建泛型类型参数并执行unitOfWork.Repository<LedgerUser>()` 来使此操作更加流畅。根据您的示例，似乎根本没有任何理由需要实例。

4. 看来您更喜欢Repository方法中的强类型而不是接口。我想也许你想要的更像是：

    public IRepository Repository()
        where T : IRepositoryEntity 
    { 
           //  your factory/cache-retrieval logic here
    }

代替

public  GenericRepository<IRepository<IRepositoryEntity>> Repository (IRepositoryEntity entity)
{
      //  your factory/cache-retrieval logic here
}

然后，如果您的调用是Repository<LedgerUser>，您的方法将返回GenericRepository<LedgerUser>，即使签名显示为IRepository<LedgerUser>。这几乎就是RepositoryProvider我建议的实现链接的工作原理。