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Teachers can raise 'dramas' which are when students forget equipment, don't do homework or are flagged for concern. Each drama for each student is stored as a separate record.

I seek a list of all unresolved dramas, grouped by student & date. So if on one day a student forgets their homework and doesn't have equipment, they come up as a single record with the properties EquipmentDrama and HomeworkDrama both set to true.

var dramas = ctx.Dramas.Where(o => !o.Resolved).Select(o => new
  {
    o.Id,
    o.StudentUsername,
    o.Student.FirstName,
    o.Student.LastName,
    o.Student.TutorGroup,
    o.Student.ClassName,
    TeacherName = o.Teacher.FirstName + " " + o.Teacher.LastName,
    o.DramaType,
    o.DateForDetention,
    o.DateHappened
  }).ToLookup(o => o.StudentUsername + o.DateHappened.ToString("ddMMyy"), o => o);
var students = dramas.Select(o => o.Key).Distinct().Select(o => dramas[o].ToList()).Select(o => new FollowUpItem
  {
    Id = String.Join(",", o.Select(d => d.Id)),
    FirstName = o[0].FirstName,
    LastName = o[0].LastName,
    TutorGroup = o[0].TutorGroup,
    EquipmentDrama = o.Any(d => d.DramaType == DramaType.Equipment),
    HomeworkDrama = o.Any(d => d.DramaType == DramaType.Homework),
    IsFlagged = o.Any(d => d.DramaType == DramaType.Flagged),
    ClassName = o[0].ClassName,
    TeacherName = o[0].TeacherName,
    DateForDetention = o[0].DateForDetention,
    DateHappened = o[0].DateHappened
  }).ToList();

Note the reason for using an anonymous type in the first LINQ statement is that I want to retrieve the related fields o.Teacher.FirstName and o.Teacher.LastName in the initial (only) database call. There must be a better way of doing this though!

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  • \$\begingroup\$ What LINQ provider are you using? Can't you just retrieve the whole Drama, Student and Teacher objects? \$\endgroup\$ – svick Apr 1 '13 at 16:06
  • \$\begingroup\$ Linq to SQL. The Person table which contains student and teacher info has lots of other fields which I don't need to retrieve. \$\endgroup\$ – James Apr 1 '13 at 16:11
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It seems like you could do this:

var results = 
    (from d in ctx.Dramas
     where !d.Resolved
     group d by new { d.Student, DateHappened = d.DateHappened.ToString("ddMMyy") } into g
     select new
     {
         Student = g.Key.Student,
         DateHappened = g.Key.DateHappened,
         EquipmentDrama = g.Any(d => d.DramaType == DramaType.Equipment),
         HomeworkDrama = o.Any(d => d.DramaType == DramaType.Homework),
         IsFlagged = o.Any(d => d.DramaType == DramaType.Flagged),
         Dramas = g.Select(d => new 
             {
                 d.Id,
                 TeacherName = d.Teacher.FirstName + " " + d.Teacher.LastName,
                 d.DateForDetention
             })
     });

NOTE: as far as I can tell, there's nothing limiting Teacher (or DateForDetention) to be the same in all grouped dramas; each drama could have a different Teacher. Here's an alternative that includes the teacher in the grouping:

var results = 
    (from d in ctx.Dramas
     where !d.Resolved
     group d by new { d.Student, d.Teacher, DateHappened = d.DateHappened.ToString("ddMMyy") } into g
     select new
     {
         Student = g.Key.Student,
         DateHappened = g.Key.DateHappened,
         EquipmentDrama = g.Any(d => d.DramaType == DramaType.Equipment),
         HomeworkDrama = o.Any(d => d.DramaType == DramaType.Homework),
         IsFlagged = o.Any(d => d.DramaType == DramaType.Flagged),
         TeacherName = d.Key.Teacher.FirstName + " " + d.Key.Teacher.LastName,
         Dramas = g.Select(d => new 
             {
                 d.Id,
                 d.DateForDetention
             })
     });

Of course, you could do the same for DateForDentention if you wanted.

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