ArcGIS Engine Developer Guide

DEVELOPING WITH ARCOBJECTS
ArcGIS applications are built using ArcObjects and can be developed via several
APIs. These include COM (VB, VC++, MainWin), .NET (VB.NET and C#),
Java, and C++. Some APIs are more suitable than others for developing certain
applications. This is briefly discussed later, but you should also read the appropriate
developer guide for the product you are working with for more information
and recommendations on which API to use.
The subsequent sections of this chapter cover some general guidelines and considerations
when developing with ArcObjects regardless of the API. Some of the
more common API languages each have a section describing the development
environment, programming techniques, resources, and other issues you must
consider when developing with ArcObjects.
For simplicity, some samples will not follow the
coding standards. For example, it is recommended
that when coding in Visual Basic, all
types defined within an ESRI object library are
prefixed with the library name, for example,
esriGeometry.IPolyline. This is only done in
samples in which a name clash will occur.
Omitting this text makes the code easier to
understand for developers new to ArcObjects.
CODING STANDARDS
Each of the language-specific sections begins with a section on coding standards
for that language. These standards are used internally at ESRI and are followed by
the samples that ship with the software.
To understand why standards and guidelines are important, consider that in any
large software development project, there are many backgrounds represented by
the team members. Each programmer has personal opinions concerning how code
should look and be built. If each programmer engineers code differently, it becomes
increasingly difficult to share work and ideas. On a successful team, the
developers adapt their coding styles to the tone set by the group. Often, this
means adapting one’s code to match the style of existing code in the system.
Initially, this may seem burdensome, but adopting a uniform programming style
and set of techniques invariably increases software quality. When all the code in a
project conforms to a standard set of styles and conventions, less time is wasted
learning the particular syntactic quirks of individual programmers, and more time
can be spent reviewing, debugging, and extending the code. Even at a social level,
uniform style encourages team-oriented, rather than individualist, outlooks—
leading to greater team unity, productivity, and ultimately, better software.
GENERAL CODING TIPS AND RESOURCES
This section on general coding tips will benefit all developers working with
ArcObjects no matter what language they are using. Code examples are shown in
VBA, however.
Class diagrams
Getting help with the object model is fundamental to successfully working with
ArcObjects. Appendix A, ‘Reading the object model diagrams’, provides a
detailed introduction to the class diagrams and shows many of the common
routes through objects. The class diagrams are most useful if viewed in the early
learning process in printed form. This allows developers to appreciate the overall
structure of the object model implemented by ArcObjects. When you are comfortable
with the overall structure, the PDF files included with the software
distribution can be more effective to work with. The PDF files are searchable;
you can use the Search dialog box in Acrobat Reader to find classes and interfaces
quickly.
70 • ArcGIS Engine Developer Guide