Creating relationship between two tables using Entity Framework

Question

I am working on some CRUD methods for a web app. I am using Entity Framework with SQL Server 2008. In particular, I have two tables that are linked using a cross reference table. It's in the following format:

• Table Tbl_Plan
  • PlanId
  • PlanNm
  • Active
• Table Tbl_Person
  • PersonId
  • PersonNm
  • PersonData
• Xref table Xref_PersonPlan
  • PersonId
  • PersonNm

Now, when I am creating a new plan I have been trying to link the two together. I'm not sure how. I know it has something to do with referencing the relationship or creating it.

The tables are set up correctly, because I can pull the data just fine once it's created (ie my sample entries in SQL Server) but creating the reference is where I am stumped. I tried the following:

using (Entities context = new Entities())
{
// TblPlan plan has already been instantiated
plan.TblPersons.Add(person);

context.AddToTblPlans(plan);

context.SaveChanges();

But obviously, the .Add() isn't what I'm looking for....help?

Answer 1

The short answer is that many-to-many relationships are not supported in LINQ to SQL the same way they are in Entity Framework and other ORMs, and you'll have to implement the desired behavior yourself.

Take a look at this article. It describes an approach that should work for you.

Answer 2

Someone just pointed me in the right direction. I should have waited ten more minutes. I was missing the.AttachTo() - I needed to attach the reference to the context before adding, since it was throwing an InvalidArgumentException.