Question

var users = from user in st.Users
            where user.UDID == cr.User.Udid
            select user;
var cityIds from city in users.First().Cities
            select city.ID;
DoSomethingWith(cityIds);

It started as this query:

select CityID from UserCities inner join User on User.ID=UserID where User.UDID=@UDID;

I can’t seem to get the join syntax right with Linq-to-Entities

Answer 1

Using query expressions isn’t really helping you here, and you wouldn’t need two of them anywehere. Here’s a direct translation:

var cityIds = st.Users
                .Where(user => user.UDID == cr.User.Udid)
                .First()
                .Cities
                .Select(city => city.ID);

Now use the fact that First can take a predicate, and you can remove the Where:

var cityIds = st.Users
                .First(user => user.UDID == cr.User.Udid)
                .Cities
                .Select(city => city.ID);