How to create an array of objects without size (without List and Dictionary)?

Question

C++ / C#

For certain reasons, I need to create arrays of objects GameObject[] ArrayObj
But I don’t always know how many there will be, as I understand it is impossible to set an array of indefinite size, also for certain reasons I don’t want to use List or Dictionary (we won’t go into details why) ...
So far I have 2 ideas how to do it:

1. Create an array with much more elements , for example, set 10 objects there and when pulling them out like this

GameObject[] ArrayObj = new GameObject[100];

foreach(GameObject obj in ArrayObj){ if(obj != null){ ........... }}

2. the same as the first option using a temporary array to calculate the length

GameObject[] ArrayObjTemp = new GameObject[100];
foreach(GameObject obj in ArrayObjTemp){ if(obj != null){ ++n }}
GameObject[] ArrayObj = new GameObject[n];
foreach(GameObject obj in ArrayObjTemp){ if(obj != null){ ArrayObj[n] = obj; ++n }}

I understand that many will say "why such bicycles", but I now need arrays of objects without List and Dictionary ...
Tell me how best to do what was planned?

Answer 1

Reading the comments - the reasons why you want to use arrays instead of List`1 are
speculation, and based on nothing.
In practice, you will not feel any difference between a List and an array in terms of memory and speed.
So take System.Collections.Generic.List<T>