Entity Framework Code First IQueryable

Question

I am using Entity Framework Code First and ran into a small road block. I have a class \"Person\" defined as such:

public class Person
{
    public Guid Id          


        

Answer 1

This question and the accepted answer are both a bit old. Code like this would, as the original question points, load the entire history for the person from the database - not good!

var results = person
    .History
    .OrderBy(h => h.OnDate)
    .Take(50)
    .ToArray();

With EF 6 there is an easy solution. Without rearranging your query, you can have it work the IQueryable way by making use of the DbContext.Entry method, the DbEntryEntity.Collection method, and the DbCollectionEntry.Query method.

var results = dbContext
    .Entry(person)
    .Collection(p => p.History)
    .Query()
    .OrderBy(h => h.OnDate)
    .Take(50)
    .ToArray();

Answer 2

Because you are querying an IEnumerable (ie: LINQ to Objects) not IQueryable (ie: LINQ to Entities) given by EF.

Instead you should use

IEnumerable<History> results = context.History.Where(h => h.Person.Id = "sfssd").OrderBy(h => h.OnDate).Take(50)