Word Replacement Program in C#

using System;
using System.IO;

class WordReplacement
{
    // Main method: entry point of the program
    static void Main(string[] args)
    {
        // Check if the correct number of arguments is provided
        if (args.Length != 3)
        {
            Console.WriteLine("Usage: replace   ");
            return; // Exit if arguments are not correct
        }

        // Extract arguments: file name, word to search, and word to replace
        string fileName = args[0];
        string searchWord = args[1];
        string replaceWord = args[2];

        // Check if the file exists
        if (!File.Exists(fileName))
        {
            Console.WriteLine("Error: The file does not exist.");
            return; // Exit if the file is not found
        }

        try
        {
            // Read the content of the file
            string content = File.ReadAllText(fileName);
            
            // Replace the occurrences of the search word with the replacement word
            string modifiedContent = content.Replace(searchWord, replaceWord);

            // Create a new file name with ".out" appended
            string newFileName = fileName + ".out";

            // Write the modified content into the new file
            File.WriteAllText(newFileName, modifiedContent);

            Console.WriteLine($"Replacement complete. The modified file is saved as {newFileName}");
        }
        catch (Exception ex)
        {
            // Catch any errors during file reading or writing and display the message
            Console.WriteLine($"An error occurred: {ex.Message}");
        }
    }
}

 Output

Usage: replace <filename> <searchword> <replaceword>

If the input file 'file.txt' contains:
"hello world, hello again"

And you run the program with the command:
replace file.txt hello goodbye

The new file 'file.txt.out' will contain:
"goodbye world, goodbye again"