Display BMP on console - Practice Exercises C# Sharp

using System; 
using System.IO;
public class DisplayPGM
{
    public static void Main(string[] args)
    {
        BinaryReader inputFile;

        string fileName = "";

        if (args.Length != 1)
        {
            Console.WriteLine("Please enter filename...");
            fileName = Console.ReadLine();
        }
        else
            fileName = args[0];


        if (!File.Exists(fileName))
        {
            Console.WriteLine("the file not exists");
            return;
        }

        try
        {
            inputFile = new BinaryReader(
                File.Open(fileName, FileMode.Open));

            // Leo cabecera 1: deber ser P5
            char tag1 = Convert.ToChar(inputFile.ReadByte());
            char tag2 = Convert.ToChar(inputFile.ReadByte());
            byte endOfLine = inputFile.ReadByte();
            if ((tag1 != 'P') || (tag2 != '5')
               || (endOfLine != 10))
            {
                Console.WriteLine("The file is not a PGM");
                inputFile.Close();
                return;
            }

            // Leo cabecera 2: ancho y alto
            byte data = 0;
            string sizeOfImage = "";
            while (data != 10)
            {
                data = inputFile.ReadByte();
                sizeOfImage += Convert.ToChar(data);
            }
            string[] widthAndHeight = sizeOfImage.Split(' ');
            int width = Convert.ToInt32(widthAndHeight[0]);
            int height = Convert.ToInt32(widthAndHeight[1]);

            // Leo cabecera 3: deber ser 255
            char maxIntensity1 = Convert.ToChar(inputFile.ReadByte());
            char maxIntensity2 = Convert.ToChar(inputFile.ReadByte());
            char maxIntensity3 = Convert.ToChar(inputFile.ReadByte());
            byte endOfLine1 = inputFile.ReadByte();
            if ((maxIntensity1 != '2') || (maxIntensity2 != '5')
               || (maxIntensity3 != '5') || (endOfLine1 != 10))
            {
                Console.WriteLine("Must be 256 grey levels");
                inputFile.Close();
                return;
            }

        }
        catch (Exception e)
        {
            Console.WriteLine("Error: {0}", e);
        }
    }
}