Command Syntax

When you first look at Visual Basic code, there are so many unrecognizable constructs that it's often difficult to tell what you're looking at. But they usually have equivalents in FoxPro.

For that reason, you should take a few minutes to go over Table 1.3 and familiarize yourself with some of the principal similarities and differences in command syntax.

Table 1.3. Command Syntax Differences

Item	Visual Basic	Visual FoxPro
Continuation character	_ ( underscore )	; (semicolon)
Comments	' (single quote)	* (asterisk) at the beginning of a line, && (two ampersands) anywhere else
Data type indicators	Deprecated in Visual Basic	{} (curly braces) around dates
Boolean literals	True False	.T. .F. or T F
String delimiters	""	"" , '' , []
Null	Nothing (the word)	.Null. or Null
Character literals	"abc"c	"abc"
Attributes of functions	<attr("value")>	No equivalent
Option Explicit On	Variables can't be used unless previously declared	No equivalent
Option Strict On	Narrowing conversions not allowed; default is Off	No equivalent
Option Compare Text	Case insensitivity	Must be explicit in FoxPro, for example, IF UPPER(a)=UPPER(b)...
Refer to class libraries	Imports (top of file)	SET CLASSLIB TO Name ADDITIVE or SET PROCEDURE TO Name ADDITIVE
Refer to base class	Inherits	ClassLibrary name shown in the Properties sheet, or declared with "as classname of sourcefilename " in code.
Namespace	Prefixes for classes	No equivalent
Array dimensioning	Dim X(2) is 3 long; X(0) is first one; all elements same type	Dim X(2) is 2 long; X(1) is first one; elements can be of different types
Array initialization	Can assign values, for example, Dim x(2) as new integer = {1,4}	DIMENSION X(2) or DECLARE X(2) , then assign individual cells ' values one line at a time
Parameters	Specified in Function or Sub statement in parentheses, with type declaration	Before Visual FoxPro7, specified in PARAMETERS or LPARAMETERS statement; beginning with Visual FoxPro7, same style as in Visual Basic .NET
Properties	Create property procedures with GET and SET methods , using a private variable as the get/set target; property name appears in Properties sheet of derived classes.	Enter the property name in the Class Designer, or assign a value to a variable name at the top of a class definition in code; the property appears immediately in the Properties sheet of the Class Designer
Default prefix block	WITH / ENDWITH	WITH / ENDWITH
Events	Used to call as yet unnamed functions in other modules	Don't have 'em, don't need 'em
Delegates	Var = AddressOf FunctionName; used to pass functions as parameters	Don't have 'em, don't need 'em
Determine variable type	TypeOf Var IS Typename or GetType()	TYPE() or VARTYPE()
Argument lists	Either positional or (Name:=Value)	Positional only
Variable or object creation	Dim VarName as Class ; VarName = New Class ; VarName = Value , or Dim VarName as New Class = Value	SET CLASSLIB TO XYZ ; VarName = CREATEOBJECT("Class") , or VarName = NEWOBJECT("Class", "Lib.VCX")
Object creation from a COM object	CreateObject("Word.Application")	CreateObject("Word.Application") or GetObject("Word.Application")
Cast operators	CTYPE()	Individual cast functions like DTOC() or STR()
Reference to container	ME	THIS , THISFORM
If statement syntax	IF Expr Then ; End If	IF Expr ; ENDIF
Case statements	Select Case VarName ; Case "abc" ; Case else ; End Select	DO CASE ; CASE Name="abc" ; OTHERWISE ; ENDCASE

This is not meant to be an exhaustive list; we'll save that for Appendix A at the end of the book, where you can find a concordance of Visual FoxPro and Visual Basic equivalents.