Linq problem with inserting new rows that have references to existing records

Question

(I believe this is the same problem as this one, but there\'s no answer there, and I think I can express the problem better here...)

I have two Linq-to-SQL classes,

Answer 1

Is the State.GetState(...) function using the same datacontext as MyDataContext.GetTable<County>()?

Answer 2

Solved!

John Boker asked:

is the State.GetState(...) function using the same datacontext as MyDataContext.GetTable() ?

My answer was "Yes" - they are using the same DataContext class... but they were using different instances.

Lesson learned: always use the same instance of your DataContext class for any objects you're planning to persist to your DB!

(John gets credit for the answer, anyway...)

Answer 3

Something isn't right here. I'm assuming State -> Count is a one to many relationship. In which case, the correct way of doing this is:

State s = State.GetState("NY"); // here I do a load of a State class via the Linq DataContext
County c = new County();
c.Name = "Rockland";

s.Counties.Add(c);
db.SubmitChanges();

Since State is the parent table, you need to add the counties to the state's counties collection.

Answer 4

If the State didn't use the same DataContext instance it might work to call the Attach method first.