ArcGIS Engine Developer Guide

DEVELOPING WITH A RCOBJECTS
Object browsers
In addition to the class diagram PDF files, the type library information can be
viewed using a number of object browsers, depending on your development
platform.
Visual Basic and .NET have built-in object browsers; OLEView (a free utility
from Microsoft) also displays type library information. The best object viewer to
use in this environment is the ESRI object viewer. This object viewer can be used
to view type information for any type library that you reference within it. Information
on the classes and interfaces can be displayed in Visual Basic, Visual C++,
or object diagram format. The object browsers can view coclasses and classes but
cannot be used to view abstract classes. Abstract classes are only viewable on the
object diagrams, where their use is solely to simplify the models.
Java and C++ developers should refer to the ArcObjects—Javadoc or ArcGIS
Developer Help.
Component help
All interfaces and coclasses are documented in the component help file. Ultimately,
this will be the help most commonly accessed when you get to know the
object models better.
For Visual Basic and .NET developers, this is a compiled HTML file that can be
viewed by itself or when using an IDE. If the cursor is over an ESRI type when
the F1 key is pressed, the appropriate page in the ArcObjects Class Help in the
ArcGIS Developer Help system is displayed in the compiled HTML viewer.
For Java and C++ developers, refer to ArcObjects—Javadoc or the ArcGIS
Developer Help system.
Code wizards
There are a number of code generation wizards available to help with the creation
of boilerplate code in Visual Basic, Visual C++, and .NET. Although these
wizards are useful in removing the tediousness in common tasks, they do not
excuse you as the developer from understanding the underlying principles of the
generated code. The main objective should be to read the accompanying documentation
and understand the limitations of these tools.
This graph shows the performance benefits of
accessing a collection using an enumerator as
opposed to the elements index. As expected, the
graph shows a classic power trend line (y=cx b ).
Indexing of collections
All collection-like objects in ArcObjects are zero based for their indexing. This is
not the case with all development environments; Visual Basic has both zero- and
one-based collections. As a general rule, if the collection base is not known,
assume that the collection base is zero. This ensures that a runtime error will be
raised when the collection is first accessed (assuming the access of the collection
does not start at zero). Assuming a base of one means the first element of a zerobased
collection would be missed and an error would only be raised if the end of
the collection were reached when the code is executed.
Chapter 4 • Developer environments • 71