Строки

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

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            string s  = System.IO.File.ReadAllText(@"data.txt");
            s += " ";
            string t =  "";
            string n = "";
            for (int i = 0;i < s.Length; i++)
            {
                if(s[i] == '.')
                {
                    t += ",";
                }
                else
                {
                    t += s[i];
                }
            }

            double[,] a = new double[1000, 3];
            int x = 0;
            int y = 0;
            for(int i = 0;i < t.Length;i++)
            {
                if (t[i] >= '0' && t[i] <= '9' || t[i] == ',')
                {
                    n += t[i];
                }
                else
                {
                    if (n.Length != 0)
                    {
                        a[x, y] = Convert.ToDouble(n);
                        y++;
                        if (y == 3)
                        {
                            y = 0;
                            x++;
                        }
                        n = "";
                    }
                }
            }
            for (int i = 0; i < x; i++)
            {
                Console.Write(a[i, 0]);
                Console.Write(" ");
                Console.Write(a[i, 1]);
                Console.Write(" ");
                Console.WriteLine(a[i, 2]);
            }


            Console.ReadKey();
        }
    }
}