Alright

How I got this error

I got one application sitting on a server

2 users accessing this application - doing some bulk data processing . eg. entering values and then the application is working with another system to extract values for them and then saving.

I can't recreate the error

The error logs show:

• The error happend at the same time in both the application
• Both happend on a Attach/Submit (but two different functions)
• There is no way they are using the same DataContext object as I save the DataContext in the HttpContext.Items

My hunch / guess is:

• One datacontext was not refreshed i.e. the an object was created for the same item twice as it was new in both the forms. eg. Customer Number - a customer was created (as one couldn't be found) by one datacontext - the other one couldn't find it either (i am using compiled queries to find it in the datacontext) so it created another object and on attaching failed.
• The HttpContext.Items lost its value somehow (i am using a virtual pc as server - maybe something went wrong there)

I am going more of the second as I can't recreate the error - but it just might be a timing (for attach/save) thing - also the error makes me think of the 2nd too.