使用实体框架加载所有子实体

Question

我有这样的数据模型

我想将对帐中的所有相关实体加载到Reconciliation对象中.

目前,我可以找到将所有相关的entites加载到单个Recon的唯一方法是多个列表.但我想加载一个Reconciliation对象中的每个相关实体.如果可能的话,优雅的方式.

Reconciliation recon = db.Reconciliations
  .Where(r => r.ReconNum == 382485).First();

List<ReconciliationDetail> reconDetails = recon.ReconciliationDetails.ToList();
List<JrnlEntryDetail> jrnlDetails = reconDetails.Select(r => r.JrnlEntryDetail).ToList();
List<JrnlEntry> jrnl = jrnlDetails.Select(j => j.JrnlEntry).ToList();

List<ARInvoice> invoices = jrnl.SelectMany(j => j.ARInvoices).ToList();
List<ARInvoiceDetail> invoicesDetail = invoices
  .SelectMany(i => i.ARInvoiceDetails).ToList();

List<ARCredMemo> credmemos = jrnl.SelectMany(j => j.ARCredMemoes).ToList();
List<ARCredMemoDetail> credmemosDetail = credmemos
  .SelectMany(c => c.ARCredMemoDetails).ToList();

List<IncomingPay> incomingPays = jrnl.SelectMany(j => j.IncomingPays).ToList();
List<IncomingPayDetail> incomingPaysDetail = incomingPays
  .SelectMany(i => i.IncomingPayDetails).ToList();

// ... and so on for outgoing pays, AP Invoices AP Cred Memo ...etc

我也试图与加载它Include和Select,但我得到这个异常:

Include路径表达式必须引用在类型上定义的导航属性.使用虚线路径作为参考导航属性,使用Select运算符作为集合导航属性.

而且我不知道如何使用Include和加载JrnlEntry的每个孩子Select

Reconciliation recon = db.Reconciliations
  .Where(r => r.ReconNum == 382485)
  .Include(r => r.ReconciliationDetails
    .Select(d => d.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry)
    .SelectMany(j => j.ARInvoices).SelectMany(i => i.ARInvoiceDetails))

编辑

管理也是这样做但它不是很漂亮:

Reconciliation recon = db.Reconciliations
.Where(r => r.ReconNum == 382485)
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.ARInvoices.Select(i => i.ARInvoiceDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.ARCredMemoes.Select(c => c.ARCredMemoDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.IncomingPays.Select(i => i.IncomingPayDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.OutgoingPays.Select(o => o.OutgoingPayDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.APInvoices.Select(o => o.APInvoiceDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.APCredMemoes.Select(o => o.APCredMemoDetails)))
  .Include(r => r.ReconciliationDetails.Select(rd => rd.JrnlEntryDetail)
    .Select(jd => jd.JrnlEntry).Select(j => j.JrnlEntryDetails))

Answer 1

有两种方法可以在Entity Framework中执行Eager Loading:

• ObjectQuery.Include方法
• 使用DbEntityEntry.Collection方法或DbEntityEntry.Reference方法及其各自的Load方法显式加载

还有一种方法可以针对数据库编写Raw SQL查询:

• DbSet.SqlQuery方法处理实体
• Database.SqlQuery方法处理任意类型
• Database.ExecuteSqlCommand用于任意DDL/DML的方法

对于这种情况,当您尝试加载几乎整个数据库时,最好对其执行专用存储过程.

Answer 2

.Include(r => r.ReconciliationDetails)最初尝试一下.然后.Select()逐个添加语句.异常再次出现在什么时候？该.SelectMany()调用看起来有点怀疑我!

第二个问题可能有助于识别问题...运行包含所有ToList()调用的代码后,您的recon实体是否完整？即它的所有导航属性是否已填充？这应该是这种情况,因为Entity Framework的自动"修复"行为.

使用EF,有时使用多个调用而不是链式Include()调用来加载复杂的对象图更有效.检查生成的SQL,看看哪种情况最有效.