Question

I have a issue I havn’t yet been able to find a solution on. To simplify the issue: I have two SQL tables and I’m using LinQ to SQL. The two tables represents Courses, where CourseType contains CourseName and TotalSpots, and CourseInstance contains CourseDate, AmountSignedUp and a refrence to CourseType. There’s a one to many relation between CourseType and CourseInstance.

Now what I need help with is the Linq query/Lambda expression to sort both CourseType and CourseInstance (if it’s posible). I want the CourseType to be sorted after how many in total free spots (calculated from every CourseInstance under CourseType; CourseType.TotalSpots – CourseInstance.SignedUp), where the CourseType with most free spots shows first. I want CourseInstance to be sorted simlar, by how many free spots that CourseInstance has (CourseType.TotalSpots – CourseInstance.AmountSignedUp).

I can’t get my head around how to solve this. I’ve looked at simlar questions and issue and this is what I’ve made so far, just to give a basic idea:

Edit: I’ve done this code so far which will sort the CourseType correctly. I’m not sure how I can get the CourseInstance sublist sorted (CourseType.CourseInstance). I guess I’ll have to do it later in the code when I’m converting it to a list unless someone has a good solution for this. I could do it as Arion suggested, why I’ll mark his answer.

var result= (
        from c in _db.CourseType
        orderby ((c.TotalSpots * c.CourseInstance.Count) - c.CourseInstance.Sum(
                                ci => (ci.AmountSignUp ?? 0))) descending
        select c
     );

Answer 1

I am not really sure what you want. But kinda sounds like you want to order by the c.TotalSpots - ci.AmountSignedUp. So is not this enough?

var result=(
    from ct in db.CourseType
    join ci in db.CourseInstance
        on ct.SomeCourseTypeKey equals ci.SomeCourseInstanceKey
    orderby c.TotalSpots - ci.AmountSignedUp
    select new {ci,ct}
    );

where db is the linq data context.

Or if c.TotalSpots and ci.AmountSignedUp is nullable then like this:

var result=(
        from ct in db.CourseType
        join ci in db.CourseInstance
            on ct.SomeCourseTypeKey equals ci.SomeCourseInstanceKey
        orderby (c.TotalSpots??0) - (ci.AmountSignedUp??0)
        select new {ci,ct}
        );

I am still not sure want you want but. You could do this:

var result=(
    from ct in db.CourseType
    orderby ct.TotalSpots
    select new 
    {
        ci,
        CourseInstances=(
            from ci in db.CourseInstance
            where ct.SomeCourseTypeKey == ci.SomeCourseInstanceKey
            orderby ct.TotalSpots- ci.AmountSignedUp
            select ci
        )
    }
    );