8.12 - Invert a text file

Objetive

Create a program to "invert" the contents of a text file: create a file with the same name ending in ".tnv" and containing the same lines as the original file but in reverse order (the first line will be the last one, the second will be the penultimate, and so on, until the last line of the original file, which should appear in the first position of the resulting file).

Hint: the easiest way, using only the programming structures we know so far, is reading the source files two times: the first time to count the amount of lines in the file, and the second time to store them in an array.


Solution

using System;
using System.IO;

namespace InvertText
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Enter name file: ");
            string fileName = Console.ReadLine();

            if (File.Exists(fileName))
            {
                StreamReader myfileRd = File.OpenText(fileName);
                string line;
                int countLines=0;
                
                // Count lines of file
                do
                {
                    line = myfileRd.ReadLine();
                    if (line != null)
                        countLines++;
                }
                while (line != null);
                myfileRd.Close();

                // Write of array of lines
                string[] lines = new string[countLines]; 
                int countLine = 0;
                myfileRd = File.OpenText(fileName);
                line = "";
                do
                {
                    line = myfileRd.ReadLine();
                    if (line != null) 
                    {
                        lines[countLine] = line;
                        countLine++;
                    }
                }
                while (line != null);
                myfileRd.Close();

                // Write of file
                StreamWriter myfileWr = File.CreateText(fileName + ".tnv");

                for (int i = lines.Length-1; i > 0; i--) 
                    myfileWr.WriteLine(lines[i]);

                myfileWr.Close();

            }
            else
                Console.WriteLine("The file no exists.");
        }
    }
}


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