在EF6 C＃中订购急切加载的导航属性数据

Question

I am Struggling to find a suitable answer that applies to to the scenario I am struggling with on StackOverflow. I am attempting to order Eager Loaded navigation property data, but I'm not sure about how to write the Linq query correctly.

My Types are as follows,

This is the parent type:

    public class Diary
{
    public Diary()
    {
        Appointments = new List<Appointment>();
    }
    public int Id{ get; set; }
    public DateTime DiaryDate { get; set; }
    public List<Appointment> Appointments { get; set; }

}

}

This is the child type:

public class Appointment
{
    public int Id { get; set; }
    public Office Office { get; set; }
    public DateTime Start { get; set; }
    public DateTime End { get; set; }
    public string Comment { get; set; }

}

The Office enum is,

public enum
{
Office1,
Office2,
Office3,
Office4
}

And my repository code that I attempted that would return an individual Diary with its linked appointments is as follows. I am not wanting to filter all of the data, I just want to be able to order the navigation property by the office num so my eventual output will look something similar to this on screen

Diary - DiaryDate

Office 1 <--office 1 appointments here-->

Office 2

<--office 2 appointments here-->

etc.

Repository code as follows

        public Diary ReturnDiaryById(int id)
    {
        using(DiaryContext context = new DiaryContext())

      {
        var returnDiary = context.Diary.AsNoTracking().Include(a => a.Issues)
        .Select(b => new Diary
        {
            Appointments = (List<Appointment>)b.Appointments.OrderBy(c => c.Office),
            Id = b.Id,
            DiaryDate = b.DiaryDate
        }

            ).FirstOrDefault();


        return returnDiary;

        }
     }

This code compiles but at runtime it compiles of a not supported exception.

I hope I have explained what I am trying to achieve and that my code roughly infers it, if not I can clarify anything,

thank you to any offers of help in advice, all input is greatly appreciated

Answer 1

Probably EF is struggling to understand the translation of your ENUM orderby to a SQL query.

In your case, there is not much performance difference between doing the ordering on the SQL side vs. doing it on the C# side.. (since we already bring in the single diary with all appointments)

So try this query and let us know if this works:

public Diary ReturnDiaryById(int id)
{
 using(var context = new DiaryContext())
 {
  var returnDiary = context.Diary.AsNoTracking().Include(a => a.Appointments)
                           .FirstOrDefault(d => d.Id == id);

  if (returnDiary != null)
  {
   returnDiary.Appointments = returnDiary.Appointments.OrderBy(c => c.Office.ToString()).ToList();
  } 

  return returnDiary ;
}