Question

I’m working on a WP7 mango App that makes use of Linq2SQL for data access.
I’m having a Note entity that has an Auto generated Key of type int.

The first time I add a new note to the db, the operation works fine, the note saves and then if I delete it from the db, it also gets removed from the db. The first entity is always of Id=0.

Then if I want to add a new note after removing the first note, I get an exception saying that the entity already exists. I concluded that the first entity with Id=0 has not been removed even though I called SubmitChanges on my data context.

Also, I’m using the same data context for data operations on my repository and on the same repository instance (a singleton for performance reasons).
To confirm that behavior, I tried to make the succession of calls and it failed !!!

this.DbContext.Notes.DeleteOnSubmit(value);
this.DbContext.SubmitChanges();
this.DbContext.Notes.InsertOnSubmit(value);
this.DbContext.SubmitChanges();

It says that it cannot add an Entity that already exists.
Any explanation for this behavior?
Thanks in advance.

Note :
When I use two different instances of the data context, this behavior disappears.

Answer 1

Well You answered your own question really at the end. Lets step through this:

1. You get the DbContext from the Database
2. Your Deleting an entry and submitting the Database(OK fine)
3. Now on this insertion your using an OLD instance of the database.

Everytime you make a

SubmitChanges();

You have update your reference, because its old.

So if you have a method that does multiple Transactions you NEED to refresh your local variable.

ONE instance of a Database should do ONE change