Question

How do I get persons whose age is over 21 using EF?

from person in context.Persons
where DateTime.UtcNow - person.Dob > TimeSpan.FromHours(184086)
select new {person, Age = DateTime.UtcNow - person.Dob}

The above failed.

What can I do to fix this? Is the above supported in the more recent version of EF eg. 4.2+

Can I access the properties of the DateTime struct as follow?

from person in context.Persons
where DateTime.UtcNow.Year - person.Dob.Year > 21
select new {person, Age = DateTime.UtcNow.Year - person.Dob.Year}

Answer 1

You can use the < operator in linq-to-entites queries. You can’t use addition or subtraction though. Fortunately, SqlFunctions has functions to calculate date differences. So what you can do is this:

var d21 = DateTime.Today.AddYears(-21);
var q = from person in context.Persons
        where person.Dob < d21
        select new
        {
            person,
            Age = SqlFunctions.DateDiff("year", person.Dob, DateTime.Today)
        }

You have to create the variable d21 first, otherwise EF complains about not knowing AddYears.