Entity Framework 6 or Core - Read query result with a "DataReader" like pattern

Question

is there a way to get a LINQ query result on a EF DBContext as a 'Typed Data Reader', in sucha a way that when i am reading de IQueryable result (ex with a .ToList()) I don't put all the result in memory?

I am expecting something like this (or equivalent):

var personQueryResult=dbContext.People.Where(…).Select(…).AsDataReader();
foreach(person in personQueryResult){
   //Here I expect that person is typed of the People Dbset<T> type, ex. a Person type and i can do:

person.Name="...";
person.Surname="...";
//etc.
}

DataReader - no. But pulling the whole result set in memory via ToList is not mandatory - treating the query as IEnumerable<T> (eventually combined with AsNoTracking) and foreach-in it is pretty much an equivalent of "entity" DataReader because you read one item at the time. — Ivan Stoev
– Ivan Stoev, Commented Aug 13, 2018 at 21:00
Oh right! Foreach on IEnumerable<T> is definitely the right approch! Thank you! — Gianluigi Liguori
– Gianluigi Liguori, Commented Aug 16, 2018 at 15:30

Gianluigi Liguori · Accepted Answer · 2018-08-16 15:50:45Z

1

There is not an explicit method that ensure you that that the collection would be scrolled trough a DbDataReader.

Knowing the inheritance hierarchy of the EF's base classes, every usage of a foreach on a DbSet<T>,IQueryable<T> or IEnumerable<T>, avoiding any direct method that will trigger a query deferred execution (ex. ToList()) will prevent to load all the records in memory so that at every "MoveNext()" of the enumerator will be used the "Read()" of the underlying DbDataReader.

answered Aug 16, 2018 at 15:50

Gianluigi Liguori

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