LINQ to Entities: Convert SQL Sub Select - entity-framework

Question

I got this figured out.
No need to answer.
The system says I have to wait 8 hours before answering my own questions. But for now the answer is below:
Here is the answer:
var startDate = DateTime.Today.AddDays(-30);
var results = (from h in Histories
join q in Quotes
on h.QuoteID equals q.QuoteID
join a in Agencies
on q.AgencyID equals a.AgencyID
where q.Status == "Inforce" &&
q.LOB == "Vacant" &&
q.EffectiveDate > startDate &&
h.Deleted == null &&
h.DeprecatedBy == null &&
h.TransactionStatus == "Committed" &&
a.DC_PLT_Roles.Any(r => r.Name == "Wholesaler")
group new {h} by new {h.PolicyNumber} into g
select new {
MaxHistoryID = g.Max (x => x.h.HistoryID),
comment = (from h2 in Histories
where h2.HistoryID == g.Max (x => x.h.HistoryID)
select h2.Comment).FirstOrDefault()
}).ToList();
The key code was:
comment = (from h2 in Histories
where h2.HistoryID == g.Max (x => x.h.HistoryID)
select h2.Comment).FirstOrDefault()
We are in the process of converting SQL / Stored Procedures to LINQ to Entities statements. And I can’t figure out the proper syntax for a sub select.
Currently I am converting this SQL:
declare #startDate DateTime
set #startDate = DATEADD(DD, -30, GETDATE())
select * from history where historyid in(
select MAX(h.historyid) as HistoryId
from History h (nolock)
inner join Quote q (nolock) on h.QuoteID = q.QuoteID
inner join Agency (nolock) a on q.AgencyID = a.AgencyID
inner join DC_PLT_EntityRoles er (nolock) on a.AgencyID = er.EntityID
inner join DC_PLT_Roles (nolock) r on er.RoleID = r.RoleID
where
q.Status = 'Inforce'
and q.LOB = 'Vacant'
and q.EffectiveDate > #startDate
and h.Deleted is null --
and h.DeprecatedBy is null --
and h.TransactionStatus = 'Committed'
and r.Name = 'Wholesaler'
group by h.PolicyNumber)
As you can see the code above is made up of two select statements. The main select (select * from history).. And a filter select (select MAX(h.historyid)…)
I got the filter select working (See below):
var startDate = DateTime.Today.AddDays(-30);
var results = (from h in Histories
join q in Quotes
on h.QuoteID equals q.QuoteID
join a in Agencies
on q.AgencyID equals a.AgencyID
where q.Status == "Inforce" &&
q.LOB == "Vacant" &&
q.EffectiveDate > startDate &&
h.Deleted == null &&
h.DeprecatedBy == null &&
h.TransactionStatus == "Committed" &&
a.DC_PLT_Roles.Any(r => r.Name == "Wholesaler")
group new {h} by new {h.PolicyNumber} into g
select new {
MaxHistoryID = g.Max (x => x.h.HistoryID)
}).ToList();
However I can’t figure out the proper syntax to set up the main select. (Basically getting the records from the History table using the HistoryID from the filter select.)
Any help would be appreciated.
Thanks for your help.

Answer 1

I figured it out, here is the code:
var startDate = DateTime.Today.AddDays(-30);
var results = (from h in Histories
.Include("Quote")
.Include("Quote.Agency")
where h.Quote.Status == "Inforce" &&
h.Quote.LOB == "Vacant" &&
h.Quote.EffectiveDate > startDate &&
h.Deleted == null &&
h.DeprecatedBy == null &&
h.TransactionStatus == "Committed" &&
h.Quote.Agency.DC_PLT_Roles.Any(r => r.Name == "Wholesaler")
group new {h} by new {h.PolicyNumber} into g
select new {
XMLData = (from h2 in Histories
where h2.HistoryID == g.Max (x => x.h.HistoryID)
select h2.XMLData).FirstOrDefault()
}).ToList();
The key logic is:
select new {
XMLData = (from h2 in Histories
where h2.HistoryID == g.Max (x => x.h.HistoryID)
select h2.XMLData).FirstOrDefault()
}).ToList();
Gotta love the Nested Query