migrating old ado.net web app to EF - entity-framework

Question

consider this query
Select (some properties from all 3 Tables)
From PageWidgets pw LEFT JOIN PageWidgetDefinition pwd
On pwd.ID = pw.WidgetID
LEFT JOIN PageWidgetSkin pws
ON pws.ID = pw.SkinInstanceID
LEFT JOIN PageWidgetSkinRows pwsr
On pwsr.SkinID = pws.ID Where pw.PageID = *x*
Order By (some properties)
in old implementation, it reads widgets on a page & their skin & i have a function looping through rows returned & make a pagewidget by its skin & its widget instance.
each widget has three row for its skin, and finally we receive a List that has everything it needs to operate
i have these classes in EF
public partial class Widget: BaseEntity {
public int ID { get; set; }
public int PageTemplateID { get; set; }
public PageTemplate PageTemplate { get; set; }
public int WidgetDefinitionID { get; set; }
public WidgetDefinition WidgetDefinition { get; set; }
public int WidgetSkinID { get; set; }
public WidgetSkin WidgetSkin { get; set; }
//other properties omitted
}
public partial class WidgetDefinition: BaseEntity {
public int ID { get; set; }
public string Title { get; set; }
//other properties omitted
public virtual ICollection<Widget> Widgets { get; set; }
}
public partial class WidgetSkin: BaseEntity {
public int ID { get; set; }
public string Name { get; set; }
//other properties omitted
public virtual ICollection<Widget> Widgets { get; set; }
public virtual ICollection<WidgetSkinRow> WidgetSkinRows { get; set; }
}
public partial class WidgetSkinRow: BaseEntity {
public int ID { get; set; }
public int WidgetSkinID { get; set; }
public virtual WidgetSkin WidgetSkin { get; set; }
}
do i need an extra bussiness layer doing the same thing?
using EF, I want to have only one trip to DB.

Answer 1

You can use "eager loading" method to do this.
Your query will then look something like this:
using (var entities = new WidgetEntities() )
{
var query = from w in entities.Widgets.Include("WidgetDefinition").Include("WidgetDefinition.Widgets").Include("WidgetSkins").Include("WidgetSkins.WidgetSkinRows")
where w.Page = *x*
order by w.someproperty
select w;
Widget myWidget = query.First();
}