Question

我正在尝试使用EF5代码优先执行数据库查找。基本结构和表关系如下;

public partial class Member
{
    public int    RecordID {get; set;}
    public string Name     {get; set;}
    ...etc.
    public virtual ICollection<MemberLink> MasterLinks {get; set;}
    public virtual ICollection<MemberLink> SlaveLinks {get; set;}
    public virtual ICollection<Message>    ReceivedMessages {get; set;}
    public virtual ICollection<Message>    SentMessages {get; set;}
}

public partial class MemberLink
{
    public int            RecordID     {get; set;}
    public virtual Member MasterMember {get; set;}
    public virtual Member SlaveMember  {get; set;}
    ...etc.
}

public partial class Message
{
    public int            RecordID  {get; set;}
    public virtual Member Sender    {get; set;}
    public virtual Member Recipient {get; set;}
    ...etc.
}

现在，我正在尝试执行的查询是使用 MemberLinkRepository ，看起来像;

public IList<MemberLink> GetMasterLinks(int p_MemberID)
{
    return Get()
           .Include ( memberLink => memberLink.MasterMember )
           .Include ( memberLink => memberLink.SlaveMember )
           .Include ( memberLink => memberLink.MasterMember.ReceivedMessages
                      .Where(
                      msg => msg.Sender.RecordID == memberLink.SlaveMember.RecordID) )
           .Where ( memberLink => memberLink.MasterMember.RecordID == p_MemberID)
           .ToList();

除了EF似乎不喜欢嵌套的Where。我可以把它分成两个独立的存储库调用（事实上，它看起来我可能不得不这样做）但是为了减少对db的调用，我试图在一次犯规中做到这一点。有谁知道如何在一个查询中实现这一目标？

我希望代码说明我正在尝试做什么......如果没有，我会尝试解释一下。

Answer 1

简短的回答是否定的，EF不允许您使用Include()。

考虑结果，如果它允许你这样做：在一种情况下，你的MemberLink.MasterMember.ReceivedMessages将被完全填充，在另一个相同的查找对象上MemberLink.MasterMember.ReceivedMessages实际上是一组消息！如果您尝试添加到ReceivedMessages会发生什么？如果添加与过滤器不匹配怎么办？这是一袋伤害。

答案是使用预测：

public IList<MemberLinkWithFiltereredMessages> GetMasterLinks(int p_MemberID)
{
    return Get()
        .Include(memberLink => memberLink.MasterMember)
        .Include(memberLink => memberLink.SlaveMember)
        .Where(memberLink => memberLink.MasterMember.RecordID == p_MemberID)
        .Select(memberLink => new MemberLinkWithFilteredMessages
        {
            MemberLink = memberLink,
            FilteredMessages = memberLink.MasterMember.ReceivedMessages
                .Where(msg => msg.Sender.RecordID == memberLink.SlaveMember.RecordID)
        })
        .ToList();
}

你真正在做的是要求一个特定的信息子集，所以要明确它。

实体框架。嵌套在.Include中

1 个答案: