If, IIf() and If()

Question

I recently asked a question about IIf vs. If and found out that there is another function in VB called If which basically does the same thing as IIf but is a short-circuit.

Does this If function perform better than the IIf function? Does the If statement trump the If and IIf functions?

Answer 1

Damn, I really thought you were talking about the operator all along. ;-) Anyway …

Does this If function perform better than the IIf function?

Definitely. Remember, it's built into the language. Only one of the two conditional arguments has to be evaluated, potentially saving a costly operation.

Does the If statement trump the If and IIf functions?

I think you can't compare the two because they do different things. If your code semantically performs an assignment you should emphasize this, instead of the decision-making. Use the If operator here instead of the statement. This is especially true if you can use it in the initialization of a variable because otherwise the variable will be default initialized, resulting in slower code:

Dim result = If(a > 0, Math.Sqrt(a), -1.0)

' versus

Dim result As Double ' Redundant default initialization!
If a > 0 Then
    result = Math.Sqrt(a)
Else
    result = -1
End If