ArcGIS Engine Developer Guide

THE V ISUAL BASIC 6 ENVIRONMENT
Use the following notation for naming variables
and constants:
[][]
describes how the variable is used or
what it contains. The and
portions should always be lowercase, and the
should use mixed case.
Library Name
Prefix
esriGeometry
c
g
m
stdole
Library
ESRI Object Library
Standard OLE COM Library
Simple variable data type
Variable scope
constant within a form or class
public variable defined in a class form or
standard module
private variable defined in a class or form
local variable
Prefix
b
by
d
fn
h
i
l
p
s
Data Type
Boolean
byte or unsigned char
double
function
handle
int (integer)
long
a pointer
string
Order of conditional determination
Visual Basic, unlike languages such as C and C++, performs conditional tests on
all parts of the condition, even if the first part of the condition is False. This
means you must not perform conditional tests on objects and interfaces that had
their validity tested in an earlier part of the conditional statement.
' The following line will raise a runtime error if pFoo is NULL.
If ((Not pFoo Is Nothing) And (TypeOf pFoo.Thing Is IBar)) then
End If
' The correct way to test this code is
If (Not pFoo Is Nothing) Then
If (TypeOf pFoo.Thing Is IBar) Then
' Perform action on IBar thing of Foo
End If
End If
Indentation
Use two spaces or a tab width of two for indentation. Since there is always only
one editor for VB code, formatting is not as critical an issue as it is for C++ code.
Default properties
Avoid using default properties except for the most common cases. They lead to
decreased legibility.
Intermodule referencing
When accessing intermodule data or functions, always qualify the reference with
the module name. This makes the code more readable and results in more efficient
runtime binding.
Multiple property operations
When performing multiple operations against different properties of the same
object, use a With … End With statement. It is more efficient than specifying the
object each time.
With frmHello
.Caption = "Hello world"
.Font = "Playbill"
.Left = (Screen.Width - .Width) / 2
.Top = (Screen.Height - .Height) / 2
End With
Arrays
For arrays, never change Option Base to anything other than zero, which is the
default. Use LBound and UBound to iterate over all items in an array.
myArray = GetSomeArray
For i = LBound(myArray) To UBound(myArray)
MsgBox cstr(myArray(i))
Next I
80 • ArcGIS Engine Developer Guide