In order to accurately get the next ID from a SharePoint list you need to access the content database for one reason: If you delete all the items from a list, and execute this simple code: list.Items[list.ItemCount -1].ID) + 1 the ID will always return 0 when in reality the real ID of the next ID will be the auto-increment number in the content database.

Note that list.Items[list.ItemCount -1].ID) + 1 will work as long as one record is always kept in the list and is never deleted.