实体框架4相关实体未加载

Question

我使用EF4中的查询，根据其中的数据通过各种其他方式（不是EF）来回拉记录和处理信息，因此我经常在列表中分离EF对象。

在这种情况下，即使我使用的是.Include（“ ...”）方法，在EntityFramework 4.0中我也没有加载相关实体的查询。

using (MyDBEntities ctx = new MyDBEntities())
{
    ctx.ContextOptions.LazyLoadingEnabled = false;

    // Get the first X records that need to be processed
    var q = (from t in ctx.DBTables
                .Include("Customer")
             let c = t.Customer
             where t.statusID == (int)Enums.Status.PostProcessing
             && c.isActive == true
             select t
            ).Take(batchSize).ToList();

    foreach (DBTable t in q)
    {
        // this results in c == null
        Customer c = t.Customer;

        // However t.CustomerID has a value, thus I know 
        // that t links to a real Customer record
        Console.WriteLine(t.CustomerID);
    }
}

任何人都可以帮助我了解为什么即使我明确声明要包括客户，也无法加载客户？

Answer 1

我找到了问题的根源！ 恶魔位于“ let”命令中。 每当我有一个let或第二个“ from”子句（如联接）时，“。includes”都会被忽略！！！

// -- THIS FAILS TO RETRIEVE CUSTOMER
// Get the first X records that need to be processed
var q = (from t in ctx.DBTables
            .Include("Customer")
         // Using a "let" like this or 
         let c = t.Customer
         // a "from" like this immediately causes my include to be ignored.
         from ca in c.CustomerAddresses
         where t.statusID == (int)Enums.Status.PostProcessing
         && c.isActive == true
         && ca.ValidAddress == true
         select t
        ).Take(batchSize).ToList();

但是，我可以一次调用就获取需要获取的ID，然后再进行第二次“获取我的包含”调用，一切正常。

// Get the first X record IDs that need to be processed
var q = (from t in ctx.DBTables
         let c = t.Customer
         from ca in c.CustomerAddresses
         where t.statusID == (int)Enums.Status.PostProcessing
         && c.isActive == true
         && ca.ValidAddress == true
         select t.TableID
        ).Take(batchSize).ToList();

// Now... go "deep-load" the records I need by ID
var ret = (from t in ctx.DBTables
            .Include("Customer")
           where q.Contains(t.TableID)
           select t);