如何创建和填充嵌套视图模型

我有一个视图模型有一些严重的嵌套。我需要从实体框架4填充它。我试图创建一个大的linq语句来填充它,但它说它不能识别.ToList()方法。它汇编得很好。运行时错误是

LINQ to Entities does not recognize the method 
'System.Collections.Generic.List`1[ProductDepartment] ToList[ProductDepartment]
(System.Collections.Generic.IEnumerable`1[ProductDepartment])' method, 
and this method cannot be translated into a store expression.

在不进行几千次数据库调用的情况下,如何更有效地填充这样的内容?

List<Product> Products {
    int ID
    string Name
    ...
    List<Department> Departments {
        int ID
        string Name
    }
    List<Image> Images {
        int ID
        string Name
    }
    List<Price> Prices {
        int ID
        string Name
        List<Version> Versions {
            int ID
            string Name
            List<Pages> Pages {
                int ID
                string Name
}   }   }   }

var myProducts = (from myProduct in DC.MyProducts
                  where p => p.productGroup == 1
                  select new Product {
                      ID = myProduct.ID,
                      Name = myProduct.Name,
                      Departments = (from myDept in DC.MyDepartments
                                     where q => q.fkey = myProduct.pkey
                                     select new Department {
                                         ID = myDept.ID,
                                         Name = myDept.Name
                                     }).ToList(),
                      ...
                      //Same field assignment with each nesting
                  }).ToList();

更新:

现在我必须对最终产品进行过滤和排序。