Performance - before using a foreach loop check if the list is empty

Question

when using a foreach loop in Unity I need to call this in the update method. So it's called once per frame...

I want to know, if it is better to check the count of the list before using the foreach loop or if it is redundant.

So I have

if (myList.Count > 0)
{
    foreach (Type type in myList)
    {
    }
}

and

foreach (Type type in myList) // no need for a check before
{
}

I could also use

for (int i = 0; i < myList.Count; i++) // use a for loop instead
{
    myList[i].DoSomething();
}

Answer 1

Unless you need some specific logic if the list is empty, then the if statement is certainly redundant. In the foreach loop if there is no data - it simply does not perform the loop.

This is more or less of a concern for best practice rather than performance though. The impact is practically non-existent; however, I think its never a bad I idea to at least be aware of these type of things.

Answer 2

The performance difference is almost certainly negligible (but it never hurts to measure).

On the other hand, a pure foreach will work for practically any collection, whereas using a for loop or checking Count (or Length or Count()) implicitly assumes that the collection is an IList.

So, you have three options that are (probably) equally performant, but one is vastly more flexible than the others.