in case like this I always used to use String.Join() method.
int[] A = { -2, 5, -1, 9, -6, 23, 67, 1, -8, 7, -3, 90 };
Console.WriteLine("\n=====================\n");
Changes(A); //<<< original index value
Console.WriteLine("\nEvery Value gets doubled");
Changes(A); //<<< new changes
static void Changes(int[] array) //<<<<<<<< methods
{
Console.WriteLine("\n=====================\n");
Console.WriteLine("{0}", String.Join(", ", array)); //<<< display orgininal values
for (int i = 0; i < array.Length; i++)
array[i] *= 2;
Console.WriteLine("{0}", String.Join(", ", array)); // <<new values
Console.WriteLine("\n=====================\n");
}