复杂的Linq集合查询

Question

我有这个DB图，想要查询以查找给定区域中的所有UserLists。提供了RegionId。

所以我可以通过这段代码获得所有部门（可能不是最好的方式......）：

var region = context.Regions.Find(regionId);
IEnumerable<Department> departments = region.Areas
            .SelectMany(a => a.Workplaces)
            .SelectMany(w => w.Departments);

帐户可以有多个用户列表，帐户可以链接到多个部门。有人可以制定一个查询来实现这个目标吗？

Answer 1

为了完整性，最终的代码是：

        List<UserList> query2 = context.Regions.Where(r => r.RegionId == regionId)
            .SelectMany(r => r.Areas)
            .SelectMany(a => a.Workplaces)
            .SelectMany(w => w.Departments)
            .SelectMany(d => d.AccountsAllowedToPost)
            .Distinct()
            .SelectMany(da => da.Lists).ToList();

Answer 2

您可以使用let语法（或.Select方法）来导航ManyToOne关系。

var query =
  from r in context.Regions
  where r.RegionId == regionId
  from a in r.Areas
  from w in a.Workplaces
  from d in w.Departments
  from da in d.DepartmentAccounts
  let acc = da.Account
  from u in acc.UserLists
  select u;


var query2 = context.Regions.Where(r => r.RegionId == regionId)
  .SelectMany(r => r.Areas)
  .SelectMany(a => a.Workplaces)
  .SelectMany(w => w.Departments)
  .SelectMany(d => d.DepartmentAccounts)
  .Select(da => da.Account)
  .SelectMany(acc => acc.UserLists);