Question

I’ve got this 3 piece of code:

 For x = 0 To sections.Length - 1
        'work
    Next
    For x = 0 To UBound(sections)
        'work
    Next
    For x = 0 To sections.GetUpperBound(0)
        'work
    Next

I’ve been thinking for about 10 minutes but I still can’t decide what exactly are the advantages of 1 choice over the other.

I was wondering if anyone has actually given this some thought and would like to share their insights. Basically I would like to know which is “better” (you can quote clarity, easy refactoring, performance, maintainability, good standard, anything that makes it “better”)

Answer 1

I’m assuming you need to use the index within the loop – otherwise, just use a For Each loop instead.

1 is the idiomatic way for a single-dimensional array, in my view. It’s the closest to the normal way you’d see in C#:

for (int x = 0; x < array.Length; x++)

It’s unfortunate that VB has this slight dual personality these days in terms of whether it’s zero or one-based. .NET is generally a zero-based platform, and you’re suffering for it here; languages designed around zero-based APIs are likely to make the “inclusive lower-bound; exclusive upper-bound” pattern simpler – whereas VB is inclusive at both ends, which is why you need the “-1”.

2 looks like it’s a VB-specific function; I would try to avoid these unless they present significant advantages, as it will make it harder for non-VB programmers (e.g. C# programmers) to understand the code. That’s only a very minor concern in many cases, but when there are no real advantages to it, I’d stick with “regular” .NET approaches.

3 is really designed for multi-dimensional (rectangular) arrays – the 0 there is saying that you want the first dimension. When you’re dealing with single-dimensional arrays it’s adding extra complexity for no good reason.

It’s possible that the first approach is also the most performant – the JIT recognizes this pattern and is able to remove some array bounds tests within the loop (it knows that x is within the bounds of the array). Now UBound may compile to IL that has the same property – I’m not sure. I suspect it makes a call to a method within the Microsoft.VisualBasic assembly, which the JIT is less likely to have knowledge of.