如何使用存储库模式加载子实体 [英] How to eager load child entities using repository pattern

问题描述

我有一个名为 Tour 的实体，可以有许多代理。我可以添加代理，但是我不能删除它们。

I have an entity named Tour which can have many Agents. I am able to add agents, but I cannot remove them.

// _repo is injected....
var tour = _repo.GetById(tourId);
tour.AddAgent(new Agent(tour.TourId));

当我尝试调用 Tour.RemoveAgent（）方法没有什么是实际删除的。我在 Tour.RemoveAgent（）方法中设置一个断点我看到 _agents 属性的数量为 0 。

When I attempt to call the Tour.RemoveAgent() method nothing is actually removed. I set a breakpoint inside the Tour.RemoveAgent() method I see that the _agents property has a count of 0.

tour.RemoveAgent(agentId); // This doesn't work because _agents is empty

我必须为EF做一些特别的事情在我的存储库中检索 Tour 时，填充 _agents 属性

Do I have to do something special for EF to populate the _agents property when I retrieve the Tour from my repository?

我决定为每个聚合创建独特的存储库，这样很容易定义什么需要包含使用 Include（）函数。这是一个例子，我继承了 GenericRepository< T> 类（也包括在这个问题的底部）。

I decided to just create a Repository unique to each aggregate, that way it is easy to define exactly what needs to be included using the Include() function. This is an example where I inherit from the GenericRepository<T> class (which is also included at the bottom of this question).

public class TourRepository : GenericRepository<Tour>
{
    public TourRepository(IDatabaseFactory databaseFactory) : base (databaseFactory)
    {
    }

    public override Tour GetById(Guid id)
    {
        return dataContext.Tours
                .Include(x => x.Agents)
                .Single(x => x.TourId == id);
    }
}

旅游课 p>

Tour Class

public partial class Tour
{
  public Guid TourId { get; private set; }
  protected virtual List<Agent> _agents { get; set; }

  public Tour()
  {
    TourId = Guid.NewGuid();
    _agents = new List<Agent>();
  }

  public void AddAgent(Agent agent)
  {
    _agents.Add(agent);
  }

  public void RemoveAgent(Guid agentId)
  {
    _agents.RemoveAll(a => a.AgentId == agentId);
  }
}

代理类 p>

Agent Class

public partial class Agent
{
  public Guid AgentId { get; private set; }
  public Guid TourId { get; private set; }
  public Tour Tour { get; private set; }

  public Agent(Guid tourId)
  {
    TourId = tourId;
    AgentId = Guid.NewGuid();
  }
}

OnModelCreating

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
  // AGENTS ============================
  modelBuilder.Entity<Agent>()
              .HasKey(x => x.AgentId)
              .Property(p => p.AgentId);

  modelBuilder.Entity<Agent>()
              .HasRequired(p => p.Tour)
              .WithMany(t => t.Agents);

  // TOURS =============================
  modelBuilder.Entity<Tour>()
              .HasKey(x => x.TourId)
              .Property(x => x.TourId);
}

资源库类

public class GenericRepository<T> : IRepository<T> where T : class {
  private MyContext dataContext;
  private readonly IDbSet<T> dbset;  

  public GenericRepository(IDatabaseFactory databaseFactory)
  {
    DatabaseFactory = databaseFactory;
    dbset = DataContext.Set<T>();
  }

  protected IDatabaseFactory DatabaseFactory
  {
    get;
    private set;
  }

  protected MyContext DataContext
  {
    get { return dataContext ?? (dataContext = DatabaseFactory.Get()); }
  }

  // ... stuff removed for brevity ...

  public T GetById(Guid id)
  {
    return dbset.Find(id);
  }
}

推荐答案

尝试使受保护的虚拟List _agents {get;组; } public

Try making protected virtual List _agents { get; set; } public

public virtual List<Agent> _agents { get; set; }

您也可以通过执行以下操作来加载：

You can also eager load by doing something like this:

_databaseContext.Tours.Include(x => x.Agents).Single(x => x.TourId == tourId) 

您可以在这里阅读更多内容：

you can read more here: http://blogs.msdn.com/b/adonet/archive/2011/01/31/using-dbcontext-in-ef-feature-ctp5-part-6-loading-related-entities.aspx

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