You don’t need the into statements:
var query =
from customer in dc.Customers
from order in dc.Orders
.Where(o => customer.CustomerId == o.CustomerId)
.DefaultIfEmpty()
select new { Customer = customer, Order = order }
//Order will be null if the left join is null
And yes, the query above does indeed create a LEFT OUTER join.
Link to a similar question that handles multiple left joins:
Linq to Sql: Multiple left outer joins