EF5 多对多更新断开连接的场景

Question

我还没有找到解决这个问题的好方法（类似的票在这里EF5 update disconnected graph (n-tier) one-to-many）。

我找到并遵循了这个例子：http://entityframeworktutorial.net/update-many-to-many-entities-in-entity-framework.aspx#.UTBeTDBhif8。

这工作得很好，但它创建了相关实体的副本（使用 sql profiler 我看到了 Insert into RelatedEntities .. 我希望只是在 MyEntities_Related 连接表上插入/更新，我不明白为什么 EF在 RelatedEntities 表上插入：(

这是我的代码：

public void AddOrUpdate(MyEntity entity) {
    var dbEntity = _context.MyEntities
      .Include(e => e.RelatedEntitis)
      .Where(e => e.ID == entity.ID)
      .SingleOrDefault();

    var newRelated = entity.RelatedEntitis.ToList<RelatedEntity>();
    var dbRelated = dbEntity.RelatedEntity.ToList<RelatedEntity>();

    _context.Entry(dbEntity).CurrentValues.SetValues(entity);

    var comparer = new EqualityComparer();
    var addedRelated = newRelated.Except(dbRelated, comparer).ToList<RelatedEntity>();
    var deletedRelated = dbRelated.Except(newRelated, comparer).ToList<RelatedEntity>();

    addedRelated.ForEach(e => dbEntity.RelatedEntity.Add(e));
    deletedRelated.ForEach(e => dbEntity.RelatedEntity.Remove(e));
}

public class EqualityComparer : IEqualityComparer<RelatedEntity>
{
    public int GetHashCode(RelatedEntity obj)
    {
      return (obj == null) ? 0 : obj.ID.GetHashCode();
    }

    public bool Equals(RelatedEntity x, RelatedEntity y)
    {
      if (ReferenceEquals(x, y)) return true;
      if (x == null || y == null) return false;
      return x.ID == y.ID;
    }
}

db 架构如下：

|------------------|
| Table MyEntities |
|------------------| 
| int ID //PK      |
|------------------| 


|--------------------------|
| Table MyEntities_Related |
|--------------------------|
| int MyEntityID           |
| int RelatedID            | 
|--------------------------|


|-----------------------|
| Table RelatedEntities |
|-----------------------|
| int RelatedID //PK    |
| string Name           | 
|-----------------------|

任何帮助表示赞赏:)

Answer 1

解决方案 我不知道它是否是最好的，但它对我有用，我认为它很有意义。 EF 创建相关实体的副本，因为它们已分离， 我以这种方式更改了我的代码：

public void AddOrUpdate(MyEntity entity) {
    var dbEntity = _context.MyEntities
      .Include(e => e.RelatedEntitis)
      .Where(e => e.ID == entity.ID)
      .SingleOrDefault();

    //replace entities with those taken from the context
    var relatedEntities = _context.RelatedEntities;
    var detachedEntities = entity.RelatedEntities;
    entity.RelatedEntities = new List<RelatedEntity>();
    foreach (var ent in detachedEntities)
    {
      entity.RelatedEntities.Add(relatedEntities .Where(e => e.ID == hop.ID).SingleOrDefault());
    }

    var newRelated = entity.RelatedEntitis.ToList<RelatedEntity>();
    var dbRelated = dbEntity.RelatedEntity.ToList<RelatedEntity>();

    _context.Entry(dbEntity).CurrentValues.SetValues(entity);
    _context.Entry(dbEntity.RelatedEntity).CurrentValues.SetValues(entity.RelatedEntitis);

    var comparer = new EqualityComparer();
    var addedRelated = newRelated.Except(dbRelated, comparer).ToList<RelatedEntity>();
    var deletedRelated = dbRelated.Except(newRelated, comparer).ToList<RelatedEntity>();

    addedRelated.ForEach(e => dbEntity.RelatedEntity.Add(e));
    deletedRelated.ForEach(e => dbEntity.RelatedEntity.Remove(e));
}