Question

Ok, lets say you have two tables: Order and OrderLine and for some reason they do not have a foreign key relationship in the database (it’s an example, live with it). Now, you want to join these two tables using Entity Framework and you cook up something like this:

        using (var model = new Model())
        {
            var orders =  from order in model.Order
                          join orderline in model.OrderLine on order.Id equals orderline.OrderId into orderlines
                          from ol in orderlines.DefaultIfEmpty()
                          select new {order = order, orderlines = orderlines};

        }

Now, the above will produce orders and orderlines, left-joined and all, but it has numerous issues:

1. It’s plain ugly
2. It returns an anonymous type
3. It returns multiple instances of the same order and I you have to do Distinct() on the client side because orders.Distinct() fails.

What I am looking for is a solution which is:

1. Pretty
2. Returns a statically well-known type instead of the anonymous type (I tried to project the query result, but I got into problems with the OrderLines)
3. Runs Distinct on the server side

Anyone?

Answer 1

Even if the database tables do not have a foreign key relationship setup, you can configure Entity Framework as if they do.

Add an OrderDetails navigation property to your Order class and then just query Orders.