Question

I am working with the following SQL query:

SELECT 
a.AppointmentId,
a.Status,
a.Type,
a.Title,
b.Days,
d.Description,
e.FormId
FROM Appointment a (nolock)
LEFT JOIN AppointmentFormula b (nolock)
ON a.AppointmentId = b.AppointmentId and b.RowStatus = 1
JOIN Type d (nolock)
ON a.Type = d.TypeId
LEFT JOIN AppointmentForm e (nolock)
ON e.AppointmentId = a.AppointmentId
WHERE a.RowStatus = 1
AND a.Type = 1
ORDER BY a.Type

I am unsure how to achieve the JOINs in LINQ. All my tables have foreign key relationships.

Answer 1

You may have to tweak this slightly as I was going off the cuff, but there are a couple of major things to keep in mind. If you have your relationships set up properly in your dbml, you should be able to do inner joins implicitly and just access the data through your initial table. Also, left joins in LINQ are not as straight forward as we may hope and you have to go through the DefaultIfEmpty syntax in order to make it happen. I created an anonymous type here, but you may want to put into a DTO class or something to that effect. I also didn’t know what you wanted to do in the case of nulls, but you can use the ?? syntax to define a value to give the variable if the value is null. Let me know if you have additional questions…

var query = (from a in context.Appointment
join b in context.AppointmentFormula on a.AppointmentId equals b.AppointmentId into temp
from c in temp.DefaultIfEmpty()
join d in context.AppointmentForm on a.AppointmentID equals e.AppointmentID into temp2
from e in temp2.DefaultIfEmpty()
where a.RowStatus == 1 && c.RowStatus == 1 && a.Type == 1
select new {a.AppointmentId, a.Status, a.Type, a.Title, c.Days ?? 0, a.Type.Description, e.FormID ?? 0}).OrderBy(a.Type);