Question

I’m working on a web project. I’m using a Sql Server 20008 R2 database via LINQ To SQL, and today I faced a very strange problem with relationships. I’ve been using them for a while and never had any problems so far.

Let’s say I have a table Stores that has the following fields: ID, Name, LastUserID where LastUserID is a “reference” to the Users table.

The Users table has the following fields: ID, Name, FavoriteStoreID where FavoriteStoreID is a “reference” to the Stores table.

So I kind of have recursive relationship.

Store.LastUser.Name // shows the name of the last user of the store

User.FavoriteStore.Name // shows the name of user's favorite store.

In Visual Studio’s designer this looks like this:

----------
-        -
- Users  -
-        -
----------


 |   / \
 |    |
 |    |
\ /   |


----------
-        -
- Stores -
-        -
----------

Now the problem is, when there are two arrows (two relationships), only one of them works. When I use the other, I get the Object reference not set to an instance of an object. error.

When I re-create the table, add that relationship (the one that raised an exception) first, it works. But when I add another one, it doesn’t work.

So obviously I messed up something, and SQL Server doesn’t understand how to interpret what I want it to do.

How can I fix this problem?

Answer 1

I’m not sure what was the problem, but I re-created the table, and now it works fine. So LINQ To SQL DOES work with circular references.