I have two tables. Table One contains a list of Areas, and Table Two contains a list of Samples, with each Sample row containing Area_ID
as a Foreign Key.
I need to retrieve all the records in my Area table with only the most recent corresponding Sample Status. I have this query, but it just returns one Area with the most recent sample from the Sample table:
var result = (
from a in db.area
join c in db.sample
on a.location_id equals c.location_id
select new
{
name = a.location_name,
status = c.sample_status,
date = c.sample_date
}).OrderByDescending(c => c.date).FirstOrDefault();
A solution could be filtering your second DbSet
:
var result = from a in db.area
join c in db.sample.Where(s=>s.location_id==a.location_id).OrderByDescending(c => c.sample_date).Take(1)
on a.location_id equals c.location_id
select new
{
name = a.location_name,
status = c.sample_status,
date = c.sample_date
};
Another solution could be applying a group join :
var result = from a in db.area
join c in db.sample
on a.location_id equals c.location_id into samples
let sample=samples.OrderByDescending(c => c.sample_date).FirstOrDefault()
select new
{
name = a.location_name,
status = sample.sample_status,
date = sample.sample_date
};
If you use navigation properties could be even easier. Supposing you have a one to many relationship between Area
and Sample
:
var result =from a in db.area
let sample= a.Samples.OrderByDescending(c => c.sample_date).FirstOrDefault()
select new
{
name = a.location_name,
status = sample.sample_status,
date = sample.sample_date
};
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