when you require to cancel all transactions on first occurance of conflict in Linq,
there are two types of ConflictMode
1)FailOnFirstConflict
2)ContinueOnConflict
you can use if somthing like given below,
db.SubmitChanges(System.Data.Linq.ConflictMode.FailOnFirstConflict);
in above code task will rollback when firstconflict will occurs.
happy coding