In Visual Basic for Applications (VBA), you can use a direct function called IIf( ) to assign a value to a variable, depending on the evaluation of a Boolean expression.
This function's syntax is
VarName = IIf(expr, truepart, falsepart)
This function is basically a one-line replacement for this If...Then...Else statement:
If expr Then VarName = truepart Else VarName = falsepart End If
VBScript doesn't have a built-in IIf( ) function. However, I've created a user-defined IIf( ) function:
Function IIf( expr, truepart, falsepart ) IIf = falsepart If expr Then IIf = truepart End Function
Because the VBScript runtime will evaluate both falsepart and truepart before passing them to the function, both expressions must be valid, even if just one will execute. For example, the code
MyVar = IIf( True, 1, 1/0 )
always produces a division by zero error, even when you confine the incorrect expression (i.e., 1/0) to falsepart, which the VBScript runtime never executes. This situation occurs because you're using a function and the VBScript runtime needs to evaluate the arguments to pass in.
In this example, using the full If...Then...Else statement is better:
If True Then VarName = 1 Else VarName = 1/0 End If
When you use the full If...Then...Else statement, VBScript evaluates an expression only if it is going to execute that expression. Thus, VBScript never evaluates the incorrect 1/0 expression, and the code executes successfully.
Learn more: Understanding VBScript: Statements