c# - 关联属性未加载到实体上

Question

我有三个相关的实体，最好用这张图来描述:

alt text http://thehashtable.com/wp-content/uploads/2010/01/Enttities.png

当我加载用户时，使用以下代码，User 对象被加载，即不为 ​​null，而是 Role 和 Department User 对象上的属性为空，尽管 User 数据库记录具有这些关联的有效 FK 值。

using (var productionEntities = new ProductionEntities())
{
    var userName = GetUserName();
    User u = (from usr in productionEntities.UserSet
              where usr.UserName == userName
              select usr).FirstOrDefault();
    if (u == null)
    {
        throw new KpiSecurityException("No local database entry found for user.") { UserName = userName };
    }
    return u.Department.DeptName;
}

旁白:我完成了整个任务只是因为 ASP.NET MembershipProvider 不支持像部门这样的用户“元数据”，而且我也不得不使用 ProfileProvider，在巨大的数据库膨胀成本。

Answer 1

您必须显式加载此属性

User u = (from usr in productionEntities.UserSet
          where usr.UserName == userName
          select usr).FirstOrDefault();

if (u == null)
{
        throw new KpiSecurityException("No local database entry found for user.") { UserName = userName };
}

if (!u.RoleReference.IsLoaded)
{ u.RoleReference.Load(); }

if (!u.DeparmentReference.IsLoaded)
{ u.DeparmentReference.Load(); }

或在您的查询中包含此实体

User u = (from usr in productionEntities.UserSet.Include("Role").Include("Department")
          where usr.UserName == userName
          select usr).FirstOrDefault();