不同的DataContext错误。为什么这是个问题?

The following code is causing a "This query contains references to items defined on a different data context" error. My 2 data contexts are created with 2 nested using blocks around the code that calls this method and displays its results on screen. The methods that this method calls only use the data context passed in to them, they don't create any of their own. I have verified that they are ok by inserting a extra return statement right before the one in the method below and I don't get any problems, which leads me to believe the problem is in the LINQ statement on the return line... What am I doing wrong?The following code is causing a "This query con