ItemUpdate class

Contains all the information related to an update of the field values for an item.

It reports all the new values of the fields.

COMMAND Subscription
If the involved Subscription is a COMMAND Subscription, then the values for the current update are meant as relative to the same key.
Moreover, if the involved Subscription has a two-level behavior enabled, then each update may be associated with either a first-level or a second-level item. In this case, the reported fields are always the union of the first-level and second-level fields and each single update can only change either the first-level or the second-level fields (but for the "command" field, which is first-level and is always set to "UPDATE" upon a second-level update); note that the second-level field values are always null until the first second-level update occurs). When the two-level behavior is enabled, in all methods where a field name has to be supplied, the following convention should be followed:

• The field name can always be used, both for the first-level and the second-level fields. In case of name conflict, the first-level field is meant.
• The field position can always be used; however, the field positions for the second-level fields start at the highest position of the first-level field list + 1. If a field schema had been specified for either first-level or second-level Subscriptions, then client-side knowledge of the first-level schema length would be required.