DeleteSet - Delete all collection instances (Ctrl+Del)
The delete set action will be activated for controls referring to owning collections, only. When the data source is not a reference or relationship or when the collection does not own its instances, the action is inactive (hidden) and cannot be called.
When list items are available read-only, the action is disabled.
When calling the action, it will delete all listed instances from the database without warning or message. In order to receive a warning message before deleting an instance the GUIFramework.Query.Delete option should be set (see "Option browser").
When a selection has been set for the list, items fulfilling the selection criteria (visible items) are removed, only.