Untitled

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp6
{
    class Program
    {
        static void Main(string[] args)
        {
            var test = Metoda2("wiersz wejsciowy");

            foreach (var item in test)
            {
                Console.WriteLine(item);
            }

            Console.ReadKey();
        }

        public static string[] Metoda2(string s)
        {
            string[] result = new string[s.Length];
            int middle = s.Length / 2;

            for (int i = 0; i < s.Length; i++)
            {

                var stringToAdd = "";
                for (int j = 0; j < s.Length; j++)
                {
                    stringToAdd += " ";
                }

                string currentSubstring = s.Substring(0, i + 1);

                stringToAdd = stringToAdd.Substring(0, middle - currentSubstring.Length / 2) + currentSubstring + stringToAdd.Substring(middle + currentSubstring.Length/2);

                result[i] = stringToAdd;
            }

            return result;
        }
    }
}