I'm sure there will be elements of your application that are of much more concern, performance-wise, than this, but it could certainly be a little more clear, or maybe a little less superfluous...
- Evaluation of and work within conditions is only required if
q > 0
- You really want to use
AndAlso to apply short-circuiting in the first condition
q > MaxQtyDisplay is redundant since this condition wouldn't hit otherwise (forgetting negative quantities but we address that by addressing my first point)Else is likewise not required.- Only get the value of
MaxQtyDisplay from the settings context once (negligible in terms of performance really, since settings are loaded from file into memory on request)
- Naming variables with single character identifiers doesn't optimise anything
So, for example, you can correct these as such:
Private Function CalculateQtyDisplay(ByVal x As Double, ByVal y As Double) As Double
Dim result = 0.0
Dim desiredQuantity As Double = x - y
Dim maxQuantity = My.Settings.MaxQtyDisplay
If (desiredQuantity > 0) Then
If (desiredQuantity <= maxQuantity) Then
result = maxQuantity
Else
result = desiredQuantity
End If
End If
Return result
End Function
Any other modifications to this code are simply going to be aesthetic and preferential really, as far as I can see. For instance you could do away with maintaining result, this goes against what I recommend in another answer but it clearly boils down to context):
Dim desiredQuantity As Double = x - y
Dim maxQuantity = My.Settings.MaxQtyDisplay
If (desiredQuantity > 0) Then
If (desiredQuantity <= maxQuantity) Then
Return maxQuantity
End If
Return desiredQuantity
End If
Return 0
A modification that comes to mind which could potentially impact performance, if anything might, is to use the IIf function available to VB.NET (both TruePart and FalsePart of this call are evaluated, though I highly doubt you'll ever have any noticeable degradation with this method anyway, even if you used this method):
Dim quantity As Double = x - y
Dim maxQtyDisplay = 1800 'My.Settings.MaxQtyDisplay
If (quantity > 0) Then
Return IIf(quantity <= maxQtyDisplay, quantity, maxQtyDisplay)
End If
Return 0
