#If...Then...#Else (directive)

Syntax 

                           #If expression Then
                           [statements]
                           [
                           #ElseIf expression Then
                           [statements]]
                           [
                           #Else
                           [statements]]
                           #End If
Description Causes the compiler to include or exclude sections of code based on conditions.
Comments The expression represents any valid BasicScript Boolean expression evaluating to TRUE of FALSE. The expression may consist of literals, operators, constants defined with #Const, and any of the following predefined constants:
Constant Value
Win32 True if development environment is 32-bit Windows.
Empty Empty
FALSE False
NULL Null
TRUE True
The expression can use any of the following operators: +, -, *, /, \, ^, + (unary), - (unary), Mod, &, =, <>, >=, >, <=, <, And, Or, Xor, Imp, Eqv.
Following are results when an expression is evaluated.
Evaluates to a: Result
Numeric value Non-zero TRUE
Zero FALSE
String not convertible to a number Type mismatch error is generated.
Null Type mismatch error is generated.
Text comparisons within expression are always case-insensitive, regardless of the Option Compare setting You can define your own constants using the #Const directive, and test for these constants within the expression parameter as shown below: 
??#Const VERSION = 2
                           Sub Main
????????#If VERSION = 1 Then
????????????directory$ = "\apps\widget"
????????#ElseIf VERSION = 2 Then
????????????directory$ = "\apps\widget32"
????????#Else
??????????MsgBox "Unknown version."
????????#End If
End Sub
Any constant not already defined evaluates to Empty. A common use of the #If...Then...#Else directive is to optionally include debugging statements in your code. The following example shows how debugging code can be conditionally included to check parameters to a function: 

                           ??#Const DEBUG = 1
                           Sub ChangeFormat(NewFormat As Integer,StatusText As String)
????????#If DEBUG = 1 Then
??????????If NewFormat <> 1 And NewFormat <> 2 Then
                           ??????????????MsgBox "Parameter ""NewFormat"" is invalid."
                           ??????????????Exit Sub
                           End If
                           ????????If Len(StatusText) > 78 Then
                           ??????????????MsgBox "Parameter ""StatusText"" is too long."
                           ??????????????Exit Sub
                           ??????????End If
????????#End If
????????Rem Change the format here...
                           End Sub
Excluded section are not compiled by BasicScript, allowing you to exclude sections of code that has errors or doesn???t even represent valid BasicScript syntax. For example, the following code uses the #If...Then...#Else statement to include a multi-line comment: 

                           Sub Main
????????#If 0
??????????The following section of code displays
                           ??????????a dialog box containing a message and an
                           ??????????OK button.
????????#End If
????????MsgBox "Hello, world."
                           End Sub
In the above example, since the expression #If 0 never evaluates to TRUE, the text between that and the matching #End If will never be compiled.
See Also #Const (directive)