Задача 3

using System;
using System.IO;
    class Program
    {
        static void Main(string[] args)
        {
            StreamReader reader = new StreamReader("D:\\text.txt");
            StreamWriter writer = new StreamWriter("D:\\text1.txt");

            string line = "";
            int numLine = 1;

            while (line != null) {


                line = reader.ReadLine();
                writer.WriteLine("{0} : {1}",numLine, line);
                numLine++;




            }

        }
    }