Search in file C# Exercise - C# Programming Course

// Import necessary namespaces
using System;  // For basic input/output operations
using System.Collections;  // For using ArrayList
using System.IO;  // For file reading operations

class Program
{
    // Main method to execute the program
    static void Main(string[] args)
    {
        // ArrayList to store the lines from the file
        ArrayList lines = new ArrayList();

        // Specify the file path (change the path as needed)
        string filePath = "textfile.txt";  // Path to the text file

        // Check if the file exists before attempting to read it
        if (File.Exists(filePath))
        {
            // Read all lines from the file and store them in the ArrayList
            string[] fileLines = File.ReadAllLines(filePath);  // Read all lines from the file

            // Add each line from the file into the ArrayList
            foreach (string line in fileLines)
            {
                lines.Add(line);  // Store each line in the ArrayList
            }

            Console.WriteLine("File loaded successfully.\n");
        }
        else
        {
            Console.WriteLine("File not found. Please make sure the file exists at the specified path.");
            return;  // Exit the program if the file is not found
        }

        // Variable to store the user's search input
        string searchTerm = "";

        // Repeat asking for a search term until the user enters an empty string
        do
        {
            // Prompt the user to enter a word or sentence to search for
            Console.Write("Enter a word or sentence to search for (or press Enter to quit): ");
            searchTerm = Console.ReadLine();  // Get the user's input

            // If the input is not an empty string, search for the term
            if (!string.IsNullOrEmpty(searchTerm))
            {
                bool found = false;  // Flag to check if any lines are found

                // Loop through all the lines in the ArrayList
                foreach (string line in lines)
                {
                    // Check if the current line contains the search term (case-insensitive search)
                    if (line.IndexOf(searchTerm, StringComparison.OrdinalIgnoreCase) >= 0)
                    {
                        // If the search term is found, display the line
                        Console.WriteLine(line);
                        found = true;  // Mark that at least one match was found
                    }
                }

                // If no matching lines were found, notify the user
                if (!found)
                {
                    Console.WriteLine("No matches found for your search.");
                }
            }

        } while (!string.IsNullOrEmpty(searchTerm));  // Continue until the user enters an empty string

        // Inform the user that the program is ending
        Console.WriteLine("Exiting the program...");
    }
}