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Reverse the Contents of a Text File in C#

This program takes a text file as input and creates a new file with the same name, but with a ".tnv" extension. The new file will contain the same lines as the original file, but in reverse order. For example, the first line from the original file will appear as the last line in the new file, and the last line will appear as the first. The program accomplishes this by first reading the file to count the number of lines and then storing the lines in an array. Once the lines are stored, they are written in reverse order to the new file. This approach makes use of basic file handling and array manipulation techniques in C#.



Group

File Handling in C#

Objective

1. The program will read the contents of a given text file.
2. It will count the number of lines in the file in the first pass.
3. In the second pass, it will store each line in an array.
4. Then, it will write the lines to a new file, starting from the last line of the array and moving to the first.
5. The new file will have the same name as the original file, with ".tnv" appended to the end.

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).

Example C# Exercise

 Copy C# Code 
using System;
using System.IO;

class ReverseFileContent
{
    // Method to reverse the contents of a text file
    public static void ReverseFile(string inputFile)
    {
        // Step 1: Read all lines from the input file
        string[] lines = File.ReadAllLines(inputFile);

        // Step 2: Create the output file with ".tnv" extension
        string outputFile = Path.ChangeExtension(inputFile, ".tnv");

        // Step 3: Open the output file to write the reversed content
        using (StreamWriter writer = new StreamWriter(outputFile))
        {
            // Step 4: Loop through the lines array in reverse order
            for (int i = lines.Length - 1; i >= 0; i--)
            {
                // Step 5: Write the reversed line to the output file
                writer.WriteLine(lines[i]);
            }
        }

        // Step 6: Inform the user that the file has been reversed and saved
        Console.WriteLine($"File reversed successfully. The output is saved as {outputFile}");
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Step 1: Ask the user for the input file name
        Console.WriteLine("Enter the name of the text file to reverse:");

        // Step 2: Get the file name from the user
        string inputFile = Console.ReadLine();

        // Step 3: Check if the file exists
        if (!File.Exists(inputFile))
        {
            Console.WriteLine("The file does not exist. Please check the file name and try again.");
            return;
        }

        // Step 4: Call the ReverseFile method to reverse the contents
        ReverseFileContent.ReverseFile(inputFile);
    }
}

 Output

//If the input file (example.txt) contains:
This is the first line.
This is the second line.
This is the third line.

//After running the program, the output file (example.tnv) will contain:
This is the third line.
This is the second line.
This is the first line.

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