gistfile1.cs

 public static class ArrayUtils
    {
        public static void Push<T>(this T[] arr, T newItem)
        {
            arr = (new T[] { newItem }).Concat(arr).ToArray();
        }

        public static T Pop<T>(this T[] arr, T newItem)
        {
            T retval = default(T);
            if (arr.Length > 0)
            {
                retval = arr[0];
                arr = arr.Skip(1).ToArray();
            }
            return retval;
        }
    }
    
class Program
    {
        static void Main(string[] args)
        {
            int[] arr = {1};
            arr.Push(1);
            arr.Push(2);
            
            foreach (var a in arr)
            {
                Console.WriteLine(a);
            }
            Console.ReadKey();
        }
    }