Question

I have the following (which I’ve used in CodeFirst):

public class MyForm
    {
        public int MyFormId { get; set; }
        //Many Form Properties
        public virtual ICollection<AuditItem> AuditItems { get; set; }
    }

public class AuditItem
    {
        public int AuditItemId { get; set; }
        public int MyFormId { get; set; }
        public IAppUser User { get; set; }
        public string ActionByUserStr { get; set; }
        public string ActionByUserDisplayName { get; set; }
        public DateTime DateOfAction { get; set; }
        public string TypeOfAction { get; set; }
        public int Step { get; set; }

        public virtual MyForm MyForm { get; set; }
    }

The AuditItem tracks many actions carried out on MyForm

I’m presenting an index page showing a table where the AuditItem’s last Step = 1.

I do an orderby DateOfAction (because the Step can get setback to 0, so I wouldn’t want it to equal 1 unless it is also the last AuditItem Record for that MyForm), then Select the last record’s step, then query on that. I want to query as early as I can so that I’m not pulling back unrequired MyForms records.

This is the query I have:

var myFormsAtStep1 =
                context.MyForms.Include("AuditItems").Where(
                    mf => mf.AuditItems.OrderBy(ai => ai.DateOfAction).Last().Step == 1);

It gives this error:

LINQ to Entities does not recognize the method 'MyForms.Models.AuditItem Last[AuditItem](System.Collections.Generic.IEnumerable`1[MyForms.Models.AuditItem])' method, and this method cannot be translated into a store expression.

Answer 1

Have a look at the list of Supported and Unsupported LINQ Methods.

Last() is not supported, but First() is, so you can just go on and reverse your ordering and use First() instead of Last().

mf => mf.AuditItems.OrderByDescending(ai => ai.DateOfAction).First().Step == 1);