List<> Better to init with a maximum capacity and only use a fraction of that, or init with no capacity

Question

I have a List<MyStruct> that I'm initializing to be empty, and I will be populating this struct in a loop as I parse the data. I know that there is a maximum possible number of entries that will be inserted into this list. For now lets say 1000. However after my parsing of the 1000 entries I may end up only putting 2 into the List. So should I initialize the List with a capacity of 1000 or don't specify a capacity and just add the few entries. It could however end up adding all 1000. What's the best way performance wise?

Answer 1

Doesn't really matter. Don't micro-optimize. Only set the capacity if you have a good idea it's roughly the amount you need. Under the hood, the list doubles every time it grows, so the number of growths is O(log(n)). It should be pretty efficient.