ArcGIS Engine Developer Guide

DEVELOPING WITH A RCOBJECTS
As an example, assume there is a variable ViewEvents that has been dimensioned
as:
Private WithEvents ViewEvents As Map
To correctly sink this event handler, you can write code within your initialization
routines like this:
set ViewEvents = MapControl1.map
DATABASE CONSIDERATIONS
When programming against the database, there are a number of rules that must
be followed to ensure that the code will be optimal. These rules are detailed
below.
If you are going to edit data programmatically, that is, not use the editing tools in
ArcMap, you need to follow these rules to ensure that custom object behavior,
such as network topology maintenance or triggering of custom feature-defined
methods, is correctly invoked in response to the changes your application makes
to the database. You must also follow these rules to ensure that your changes are
made within the multiuser editing (long transaction) framework.
Edit sessions
Make all changes to the geodatabase within an edit session, which is bracketed
between StartEditing and StopEditing method calls on the IWorkspaceEdit interface
found on the Workspace object.
This behavior is required for any multiuser update of the database. Starting an
edit session gives the application a state of the database that is guaranteed not to
change, except for changes made by the editing application.
In addition, starting an edit session turns on behavior in the geodatabase such that
a query against the database is guaranteed to return a reference to an existing
object in memory if the object was previously retrieved and is still in use.
This behavior is required for correct application behavior when navigating between
a cluster of related objects while making modifications to objects. In other
words, when you are not within an edit session, the database can create a new
instance of a COM object each time the application requests a particular object
from the database.
Edit operations
Group your changes into edit operations, which are bracketed between the
StartEditOperation and StopEditOperation method calls on the IWorkspaceEdit interface.
You may make all your changes within a single edit operation if so required. Edit
operations can be undone and redone. If you are working with data stored in
ArcSDE, creating at least one edit operation is a requirement. There is no additional
overhead to creating an edit operation.
74 • ArcGIS Engine Developer Guide