ArcGIS Engine Developer Guide

DEVELOPING WITH A RCOBJECTS
Recycling and nonrecycling cursors
Use nonrecycling search cursors to select or fetch objects that are to be updated.
Recycling cursors should only be used for read-only operations, such as drawing
and querying features.
Nonrecycling cursors within an edit session create new objects only if the object
to be returned does not already exist in memory.
Fetching properties using query filters
Always fetch all properties of the object; query filters should always use “*”. For
efficient database access, the number of properties of an object retrieved from
the database can be specified. For example, drawing a feature requires only the
OID and the Shape of the feature; hence, the simpler renderers only retrieve these
two columns from the database. This optimization speeds up drawing but is not
suitable when editing features.
If all properties are not fetched, then object-specific code that is triggered may
not find the properties that the method requires. For example, a custom feature
developer might write code to update attributes A and B whenever the geometry
of a feature changes. If only the geometry was retrieved, then attributes A and B
would be found to be missing within the OnChanged method. This would cause
the OnChanged method to return an error, which would cause the Store to return
an error and the edit operation to fail.
Marking changed objects
After changing an object, mark the object as changed (and ensure that it is updated
in the database) by calling Store on the object. Delete an object by calling
the Delete method on the object. Set versions of these calls also exist and should
be used if the operation is being performed on a set of objects to ensure optimal
performance.
Calling these methods guarantees that all necessary polymorphic object behavior
built into the geodatabase is executed (for example, updating of network topology
or updating of specific columns in response to changes in other columns in
ESRI-supplied objects). It also guarantees that developer-supplied behavior is
correctly triggered.
Update and insert cursors
Never use update cursors or insert cursors to update or insert objects into object
and feature classes in an already-loaded geodatabase that has active behavior.
Update and insert cursors are bulk cursor APIs for use during initial database
loading. If used on an object or feature class with active behavior, they will
bypass all object-specific behavior associated with object creation, such as topology
creation, and with attribute or geometry updating such as automatic recalculation
of other dependent columns.
Chapter 4 • Developer environments • 75