How to do a single line If statement in VBScript for Classic-ASP?

Question

The \"single line if statement\" exists in C# and VB.NET as in many other programming and script languages in the following format

lunchLocation = (dayOfTheW         


        

Answer 1

edited 2017/01/28 to adapt to some of the non boolean condition arguments

Note: If all you need is to select an string based on an boolean value, please, use the code in the Polinominal's answer. It is simpler and faster than the code in this answer.

For a simple but more "flexible" solution, this code (the original code in this answer) should handle the usual basic scenarios

Function IIf( Expression, TruePart, FalsePart)
Dim bExpression
    bExpression = False 
    On Error Resume Next
    bExpression = CBool( Expression )
    On Error Goto 0
    If bExpression Then 
        If IsObject(TruePart) Then 
            Set IIf = TruePart
        Else 
            IIf = TruePart
        End If 
    Else
        If IsObject(FalsePart) Then 
            Set IIf = FalsePart
        Else 
            IIf = FalsePart
        End If 
    End If 
End Function 

If uses the Cbool function to try to convert the passed Expression argument to a boolean, and accepts any type of value in the TrueValue and FalseValue arguments. For general usage this is fast, safe and fully complies to documented VBScript behaviour.

The only "problem" with this code is that the behaviour of the CBool is not fully "intuitive" for some data types, at least for those of us that constantly change between vbscript and javascript. While numeric values are coherent (a 0 is a False and any other numeric value is a True), non numeric types generate a runtime error (in previous code handled as false), except if it is a string with numeric content or that can be interpreted as true or false value in english or in the OS locale.

If you need it, a VBScript version "equivalent" to the ? javascript ternary operator is

Function IIf( Expression, TruePart, FalsePart )
Dim vType, bExpression 

    vType = VarType( Expression )
    Select Case vType
        Case vbBoolean                : bExpression = Expression 
        Case vbString                 : bExpression = Len( Expression ) > 0
        Case vbEmpty, vbNull, vbError : bExpression = False
        Case vbObject                 : bExpression = Not (Expression Is Nothing)
        Case vbDate, vbDataObject     : bExpression = True
        Case Else
            If vType > 8192 Then 
                bExpression = True
            Else
                bExpression = False 
                On Error Resume Next
                bExpression = CBool( Expression )
                On Error Goto 0
            End If 
    End Select 

    If bExpression Then 
        If IsObject( TruePart ) Then 
            Set IIf = TruePart
        Else 
            IIf = TruePart
        End If 
    Else
        If IsObject( FalsePart ) Then 
            Set IIf = FalsePart
        Else 
            IIf = FalsePart
        End If 
    End If 
End Function 

BUT independently of the version used, be careful, you are calling a function, not using a ternary operator. Any code, or function call you put in TruePart of FalsePart WILL BE EXECUTED independently of the value of the condition. So this code

value = IIf( 2 > 3 , DoSomething(), DontDoSomething() )

WILL EXECUTE the two functions. Only the correct value will be returned to value var.