Entity Framework - Performance in count

Question

I\'ve a little question about performance with Entity Framework.

Something like

using (MyContext context = new MyContext())
{
    Document DocObject         


        

Answer 1

Your first query isnt fully transalted to sql - when you call .ToList().Count(), you are basically saying "download all, materialize it to POCO and call extension method named Count()" which, of course, take some time.

Your second query is, however, transalted to something like select count(*) from Documents where GroupId = @DocObjectGroup which is much faster to execute and you arent materializing anything, just simple scalar.