Linq join on two values

Question

Suppose I have a list of {City, State}. It originally came from the database, and I have LocationID, but by now I loaded it into memory. Suppose I also have a t

Answer 1

Well, there isn't a lot more that you can do, as long as you rely on a table lookup, the only thing you can do to speed up things is to put an index on City and State.

The linq statement has to translate into a valid SQL Statement, where "Any" would translate to something like :

SELECT * FROM Restaurants where City in ('...all cities')

I dont know if other ORM's give better performance for these types of scenarios that EF, but it might be worth investigating. EF has never had a rumor for being fast on reads.

Edit: You can also do this:

List<string> names = new List { "John", "Max", "Pete" };
bool has = customers.Any(cus => names.Contains(cus.FirstName)); 

this will produce the necessary IN('value1', 'value2' ...) functionality that you were looking for

Answer 2

It seems to me that you need this:

var establishments =
    from r in restaurants
    join l in locations.Where(x => x.LocationId == id)
        on new { r.City, r.State } equals new { l.City, l.State } into gls
    select r;