了解LINQ与SQL的关联

Question

Im trying to understand how to use the associations(so that my linq statements are more readable)

I have a table logs, which has many mapping IDs. I have a table with a primary key mapping ID which has permutations of countryID, categoryID, and categoryTypeID. Each of those has that column as a primary key on each of there tables. My understanding is that if i set up my context right i could do something like

(from l in datacontext.logs
where l.mappings.category.barId== myNumber
select l)

But I cant seem to figure out how to make that happen. Is it possible, and how could i go about setting up my project to do this.

Answer 1

Can you not use

(from l in datacontext.logs
join m in datacontext.mappings on l.mappingId equals l.mappingid
join c in datacontext.category on m.categoryid equals c.categoryid
where c.barId == myNumber
select l).ToList();

I am making assumptions on your table structure based on your question.

Answer 2

I figured it out, my associations were backwards. logs is not the parent of mapings, rather mapings is the parent of logs.