ArcGIS Engine Developer Guide

THE V ISUAL BASIC 6 ENVIRONMENT
The tables below summarize suggested naming
standards for the various elements of your Visual
Basic projects.
Module Type
Form
Class
Standard
Project
Prefix
frm
Name your modules according to the overall
function they provide; do not leave any with
default names (such as “Form1”, “Class1”, or
“Module1”). In addition, prefix the names of
forms, classes, and standard modules with three
letters that denote the type of module, as shown
in the table above.
Control Type
Check box
Combo box
Command button
Common dialog
Form
Frame
Graph
Grid
Image
Image list
Label
List box
List view
Map control
Masked edit
Menu
OLE client
Option button
Picture box
Progress bar
Rich text box
Scroll bar
Slider
Status bar
Tab strip
Text box
Timer
Tool bar
Tree view
cls
bas
prj
Prefix
chk
cbo
cmd
cdl
frm
fra
gph
grd
img
iml
lbl
lst
lvw
map
msk
mnu
ole
opt
pic
pbr
rtf
srl
sld
sbr
tab
txt
tmr
tbr
tvw
As with modules, name your controls according
to the function they provide; do not leave them
with default names since this leads to decreased
maintainability. Use the three-letter prefixes
above to identify the type of control.
USER INTERFACE STANDARDS
Consider preloading forms to increase the responsiveness of your application. Be
careful not to preload too many (preloading three or four forms is fine).
Use resource files (.res) instead of external files when working with bitmap files,
icons, and related files.
Make use of constructors and destructors to set variable references that are only
set when the class is loaded. These are the VB functions: Class_Initialize() and
Class_Terminate() or Form_Load() and Form_Unload(). Set all variables to Nothing
when the object is destroyed.
Make sure the tab order is set correctly for the form. Do not add scroll bars to the
tabbing sequence; it is too confusing.
Add access keys to those labels that identify controls of special importance on the
form (use the TabIndex property).
Use system colors where possible instead of hard-coded colors.
Variable declaration
• Always use Option Explicit (or turn on Require Variable Declaration in the VB
Options dialog box). This forces all variables to be declared before use and,
thereby, prevents careless mistakes.
• Use Public and Private to declare variables at module scope and Dim in local
scope. (Dim and Private mean the same at Module scope; however, using Private
is more informative.) Do not use Global anymore; it is available only for
backward compatibility with VB 3.0 and earlier.
• Always provide an explicit type for variables, arguments, and functions.
Otherwise, they default to Variant, which is less efficient.
• Only declare one variable per line unless the type is specified for each variable.
This line causes count to be declared as a Variant, which is likely to be unintended.
Dim count, max As Long
This line declares both count and max as Long, the intended type.
Dim count As Long, max As Long
These lines also declare count and max as Long and are more readable.
Dim count As Long
Dim max As Long
Parentheses
Use parentheses to make operator precedence and logic comparison statements
easier to read.
Result = ((x * 24) / (y / 12)) + 42
If ((Not pFoo Is Nothing) And (Counter > 200)) Then
Chapter 4 • Developer environments • 79