Converting T-SQL to Linq - tsql

Question

I am using Entitry Framework 4.1 and I am struggling to understand how the convert the below query which uses joins and aggregate methods to a Linq to Entities call in the DomainService.
SELECT tblTime.Period As Timeline, COUNT(tblEngineeringDashboard_ItemList.ID) AS Items
FROM tblEngineeringDashboard_ItemList INNER JOIN
tblTime ON tblEngineeringDashboard_ItemList.TimeID = tblTime.ID
GROUP BY tblTime.Period
ORDER BY tblTime.Period
Can anyone provide help.
Possible Solution
Dim var = From i In ObjectContext.tblEngineeringDashboard_ItemList
Join t In ObjectContext.tblTimes On i.TimeID Equals t.ID
Group By i.TimeID Into Group
Select DateStart = (From n In ObjectContext.tblTimes Where n.ID = TimeID Select n.Period), PartCount = Group.Count
Phil

Answer 1

The first thing which comes to mind is:
var q = from t in Context.Time
group t by t.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = (from ti in g
from il in ti.ItemList // or whatever the property for the navigation to tblEngineeringDashboard_ItemList is called
select il).Count()
};
However, the original SQL had an INNER JOIN, which would reject tblTime records without any matching records in tblEngineeringDashboard_ItemList. So you may want:
var q = from t in Context.Time
where t.ItemList.Any()
group t by t.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = (from ti in g
from il in ti.ItemList // or whatever the property for the navigation to tblEngineeringDashboard_ItemList is called
select il).Count()
};
You can also flip the query around:
var q = from i in Context.EngineeringDashboardItemList
where i.Time != null
group i by i.Time.Period into g
orderby g.Key
select new
{
Timeline = g.Key,
Items = g.Count()
};

Answer 2

Does this work?
tblEngineeringDashboard_ItemList
.Join(tblTime,ed => ed.TimeID ,t => t.ID, (ed,t) => new{ed,t})
.GoupBy(g => g.t.Period)
.Select(s => new
{
Timeline = s.Key,
Items = s.Count()
}
)
.OrderBy(o => o.Timeline)

Answer 3

While converting from sql to linq isn't an ideal approach (you should think directly in linq, translating your need to a linq query), the query you posted is rather simple.
var grouped = tblTime.OrderBy(c => c.Period).GroupBy(c => c.Period).Select(c =>
new {
timeline = c.Key,
count = c.SelectMany(x => x.tblEngineeringDashboard).Count()
});
*Edit: There, fixed. Everything on the L2E engine.
This provided that there are correct foreign keys between the tables (thus you don't have to declare the join manually).