Passing grouped linq object to view

Question

Im trying to pass a linq list object from my controller to my view. The linq object contains a grouping which is throwing some sort of error. I just want to display the grouped objects in a view. The linq statement works perfectly but displaying the statement doesn't! any help would be greatly appreciated!

controller

        public ViewResult StudentAttendanceForYear(int id)
    {

        DateTime finDate = System.DateTime.Today;
        DateTime strtDate = DateTime.Today.AddMonths(-6);


        var chosenStudent = (from t in db.ClassInstanceDetails.Include("Student")
                                 where (t.Attendance == false) && (t.StudentID == id)
                                 && (t.ClassInstance.Date > strtDate) && (t.ClassInstance.Date < finDate)
                                 group t by new { t.ClassInstance.Date.Year, t.ClassInstance.Date.Month, t.ClassInstance.Date.Day } into grp
                                 select new
                                 {

                                     absentDate = grp.Key,
                                     numAbsences = grp.Count(t => t.Attendance == false)

                                 }).ToList();



        return View(chosenStudent.ToList());
    }

view

I tried changing my view to

@model IEnumerable<System.Linq.IGrouping<object, FYPSchoolApp.DAL.ClassInstanceDetail>>

but still no luck, and I keep getting the following error:

The model item passed into the dictionary is of type 'System.Collections.Generic.List1[<>f__AnonymousType72[<>f__AnonymousType63[System.Int32,System.Int32,System.Int32],System.Int32]]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable1[System.Linq.IGrouping`2[System.Object,FYPSchoolApp.DAL.ClassInstanceDetail]]'.

Answer 1

Don't try to pass anonymous types into the view as a model.

What you need is a ViewModel:

public class AbsentCountViewModel
{
   public DateTime absentDate { get; set; }
   public int numAbsences { get; set; }
}

Then change your query to select into your viewmodel

var chosenStudent = 
   (from t in ...
   group t by new 
   { 
           t.ClassInstance.Date.Year, 
           t.ClassInstance.Date.Month, 
           t.ClassInstance.Date.Day 
   } into grp
   select new
   {
       absentDate = grp.Key,
       numAbsences = grp.Count(t => t.Attendance == false)
   }).ToList()
   // you need to do the select in two steps 
   // because EF cannot translate the new DateTime
   .Select(item => new AbsenctCountViewModel
   {
       absentDate = new DateTime(item.absentDate.Year, 
                                 item.absentDate.Month, 
                                 item.absentDate.Day)
       numAbsences = item.numAbsences
   }).ToList();

return View(chosenStudent);

And finally you can access your result in the view with the @model:

@model List<AbsenctCountViewModel>