When we import or export a table from sqlserver database to another table in sqlserver database, the "identity specification" switch to NO from YES. therefore we try to switch back from NO to YES but a message appears in sqlserver, indicating that: "Saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created. You have either made changes to a table that can't be re-create or enabled the option Prevent saving changes that require the table to be re-create."
So what should I do to have identity specification to remain YES or I be able to switch it from NO to YES.