Does LINQ to SQL support Single Unit of work only or can I persist the Context and do Next operation?

I have a开发者_如何学编程 windows application. I am trying to insert a record through a DataContext. It has Unique identifier in the table. Even I am executing a trigger after insertion. So I am making a select query in the end of the trigger to get the auto generator number and to avoid auto-sync error. As it's a windows application I can keep the Context for longtime. When I create a new object ( for example order) and do the same previous operation, upon SubmitChanges operation, it shows cannot have duplicate key. Why can't I use this same Context to Insert the second record? Or do I need to create a new Context to insert a new Record?(Does this Unit of work Concept comes here?). Creating new Context is bad idea as I need to load all data again..

Any thought?

Some code sample to explain my situation:

CallCenterLogObjCotext = (CallCenterLogObjCotext == null ? (new CallcenterLogContext) : (CallCenterLogObjCotext));

 CallDetail newCallDetailsOpenTicket = new CallDetail();

 newCallDetailsOpenTicket.CallPurpose = (from callpuposelist in CallCenterLogObjCotext.CallPurposes
   where callpuposelist.CallPurposeID == ((CallPurpose)(cbcallpurpose.SelectedItem)).CallPurposeID
   select callpuposelist).FirstOrDefault();

Lots of settings like this ...

CallCenterLogObjCotext.CallDetails.InsertOnSubmit(newCallDetailsOpenTicket);
CallCenterLogObjCotext.SubmitChanges();

As I mentioned above, this is a click on Open Ticket button on windows form. I change the values of fname, lname and all in the textboxes available on that form and clicked the same button. So it will call the same method again. I get the below specified error:

System.Data.Linq.DuplicateKeyException: Cannot add an entity with a key that is already in use.

You can insert more than one row with the same context object, see http://weblogs.asp.net/scottgu/archive/2007/05/19/using-linq-to-sql-part-1.aspx, http://msdn.microsoft.com/en-us/library/bb425822.aspx, and other numerous online examples. The duplicate key issue could be a linq to sql configuration issue, or a database integrity error, i.e. such as if you have a natural primary key on a table and are trying to insert a row with the same natural primary key more than once.