LINQ2SQL Exception: The query contains references to items defined on a different data context

When getting the exception

The query contains references to items defined on a different data context.

Check that the context object being used for each 'from' and 'join', etc, within LINQ statements is not a new object but the same one being re-used!

• http://stackoverflow.com/questions/3478148/two-linq-data-contexts-proving-a-problem