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Conditionally compiles selected blocks of Visual Basic code.
#If expression Then statements [ #ElseIf expression Then [ statements ] ... #ElseIf expression Then [ statements ] ] [ #Else [ statements ] ] #End If
On the surface, the behavior of the #If...Then...#Else directives appears the same as that of the If...Then...Else statements. However, the #If...Then...#Else directives evaluate what is compiled by the compiler, whereas the If...Then...Else statements evaluate conditions at run time.
Conditional compilation is typically used to compile the same program for different platforms. It is also used to prevent debugging code from appearing in an executable file. Code excluded during conditional compilation is completely omitted from the final executable file, so it has no effect on size or performance.
Regardless of the outcome of any evaluation, all expressions are evaluated using Option Compare Binary. The Option Compare statement does not affect expressions in #If and #ElseIf statements.
No single-line form of the #If, #Else, #ElseIf, and #End If directives exists. No other code can appear on the same line as any of the directives.
This example uses the #If...Then...#Else construct to determine whether to compile certain statements.