[Solved]-Entity Framework object limitations in aggregate LINQ query-LINQ,C#

you can only use supported members in l2e queries, and date isn't one of those.

one workaround is to break your single l2e query into one l2e query followed by one linq to objects query:

var q = from e in context.entities
        select new
        {
            id = e.id,
            datetime = e.datetime
        };

var r = from e in q.asenumerable()
        select new
        {
            id = e.id,
            date = e.datetime.date
        };