can we make array of interface object in c# .net code example

Example 1: hwo to make an array in C#

int[] Nameofarray = new int[how much is the max];

for example:
int[] X = new int[5];

Example 2: how i can add dynamic value in string in javascript

const poem = "The Wide Ocean";
const author = "Pablo Neruda";

const favePoem = `My favorite poem is ${poem} by ${author}.`;