how to add to an array c#

List<int> add_list= new List<int>();
for (int i = 0; i < 400; i++)
{
   add_list.Add(value);
}
int[] arrayOfNumbers = new int[400];
for (int index = 0; runs < 400; runs++)
{
  	// Using array[index], you can modify the value at that index
    arrayOfNumbers[index] = value;
}// To add a value to a C# array, use 'Add()'
List<string> ls = new List<string>();
ls.Add("Hello");List<int> termsList = new List<int>();
for (int runs = 0; runs < 400; runs++)
{
    termsList.Add(value);
}

// You can convert it back to an array if you would like to
int[] terms = termsList.ToArray();