如何转换IQueryable <Int> &#39;int&#39;

Question

I am facing a problem when trying to get the last record of my model Client in terms of the userID.

var user_id = (int)Membership.GetUser().ProviderUserKey;
        var client_id = from d in db.Connexions 
                        where d.userId == user_id
                        select d.ClientID;

        var lastClient = from d in db.Clients
                         where d.ClientID = client_id // here appears the error
                         select d;

For the first one there is no error but for the second request there is an error of type

Answer 1

var client_id = (from d in db.Connexions 
            where d.userId == user_id
            select d.ClientID).First();

Answer 2

If you want to retrieve last record then do this :

var lastClient = (from d in db.Clients
                  where d.ClientID == client_id  <--- //here it should be "==" not "="
                  orderby d.UpdateTime descending
                  select d).FirstOrDefault();

Answer 3

This code:

var client_id = from d in db.Connexions 
                    where d.userId == user_id
                    select d.ClientID;

does not return a single int, but a lazy collection of ints fulfilling the conditions given. client_id.First() will give you the first id in that collection.