Cambiador de texto Ejercicio C# - Curso de Programación C# (C Sharp)

using System;
using System.IO;
namespace Replace
{
    class Program
    {
        static void Main(string[] args)
        {
            ReplaceTextFile("file.txt", "Hola", "hola");
        }

        public static void ReplaceTextFile(string urlFile, string textReplace, string newText)
        {
            StreamReader myfileRd = File.OpenText(urlFile); ;
            StreamWriter myfileWr = File.CreateText("file.txt.out"); ;
            string line = " ";
            do
            {
                line = myfileRd.ReadLine();
                if (line != null)
                {
                    line = line.Replace(textReplace, newText);
                    myfileWr.WriteLine(line);
                }
            }
            while (line != null);
            myfileWr.Close();
            myfileRd.Close();
        }
    }
}