LINQ-to-SQL retrieving data from a different query!

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+1 Q:

LINQ-to-SQL retrieving data from a different query!

I have a web application that uses LINQ-to-SQL. It has a very strange issue, where a LINQ command retrieves the data that is supposed to be returned by another, totally different query that runs in a different thread. What could be the cause of this?

Specifically, a user accesses the application from his machine, opening a certain page. At the same time, another user accesses a different page from his (different) machine. One of the queries throws an exception, while the other returns the data of the first one, which comes from a very different table!

The case is always reproducible, whenever we stress the application with these two users. I've checked but I don't see any shared variables of any kind. What else could the problem be? What should I be looking for?

Your help is really appreciated.

+1 A:

Sounds like a connection is being reused. Make sure not to cache those and always create and release them properly, such as in this sample.

Lucero 2010-06-28 15:10:41

That's what I've been trying to investigate most of the day, but in vain. I've even tried to create a new `DataContext` with every request (for one of the pages), but this didn't correct the issue. Do you have a suggestion on where else to look?

Hosam Aly 2010-06-28 15:39:33

You don't want to re-create the `DataContext` on each call, as this should pretty much be a "singleton". That said, what code you you use to connect to the database?

Lucero 2010-06-28 15:54:24

The `DataContext` used to be injected (using Unity), but I just changed it for the purposes of testing. To connect to the database I simply create a `DataContext` with a `SqlConnection` that takes the connection string. However, there is another (older) part of the application that use ADO.NET directly, every time creating (and closing) a new connection.

Hosam Aly 2010-06-29 09:03:26

Are you re-creating the connection for each call? If not, that is your problem. From the `DataContext` constructor MSDN docs: *A `DataContext` opens and closes a database connection as needed if you provide a closed connection or a connection string. In general, you should never have to call `Dispose` on a `DataContext`. If you provide an open connection, the `DataContext` will not close it. Therefore, do not instantiate a DataContext with an open connection unless you have a good reason to do this.*

Lucero 2010-06-29 14:44:18

You sure this isn't a session issue rather than a linq issue? Data requested from one asp.net session but passed over to another sounds like something's getting mixed up there.

Frank Tzanabetis 2010-06-29 16:49:44

ansaurus

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LINQ-to-SQL retrieving data from a different query!

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