Reading a binary file (1: BMP) C# Exercise - C# Programming Course

// Importing necessary namespaces for file handling
using System;
using System.IO;

public class BMPChecker
{
    // Method to check if a BMP file starts with "BM"
    public static bool IsBMPFileValid(string filePath)
    {
        // Using FileStream to read the binary content of the file
        using (FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            // Checking if the file has at least two bytes to read
            if (fileStream.Length < 2)
            {
                // Returning false if file size is less than 2 bytes
                return false;
            }

            // Reading the first two bytes from the file
            int firstByte = fileStream.ReadByte();
            int secondByte = fileStream.ReadByte();

            // Checking if the first two bytes are 'B' (0x42) and 'M' (0x4D)
            return (firstByte == 0x42 && secondByte == 0x4D);
        }
    }
}

// Auxiliary class with Main method for testing the BMPChecker functionality
public class Program
{
    public static void Main(string[] args)
    {
        // Variable to store the file path
        string filePath;

        // Checking if the file path is provided as an argument
        if (args.Length == 1)
        {
            // Assigning the argument to the filePath variable
            filePath = args[0];
        }
        else
        {
            // Prompting the user for the file path if not provided as an argument
            Console.Write("Enter the BMP file path: ");
            filePath = Console.ReadLine();
        }

        // Checking if the specified file exists
        if (File.Exists(filePath))
        {
            // Calling the IsBMPFileValid method to validate the BMP file
            bool isValidBMP = BMPChecker.IsBMPFileValid(filePath);

            // Displaying the result to the user
            if (isValidBMP)
            {
                Console.WriteLine("The file appears to be a valid BMP image.");
            }
            else
            {
                Console.WriteLine("The file does not appear to be a valid BMP image.");
            }
        }
        else
        {
            // Displaying an error message if the file does not exist
            Console.WriteLine("The specified file does not exist.");
        }
    }
}