Question

Create a method that determines whether a string is a valid hex

code. A hex code must begin with a pound key # and is exactly 6

characters in length. Each character must be a digit from [0-9] or

an alphabetic character from A-F . All alphabetic characters may

be uppercase or lowercase.

Answer 1

using System;

namespace HexCodeValid
{
    class Program
    {
        public static string Valid_hex(string hexcode)
        {
            string str = "ABCDEFabcdef";
            if (hexcode[0] != '#')
                return "A hex code must begin with a pound key #";
            else if (hexcode.Length != 6)
                return "A hex code must 6 characters in length";
            else
            {
                for(int i=1; i < 6; i++)
                {
                    if ((Char.IsNumber(hexcode[i]) == false) && (str.Contains(hexcode[i].ToString()) == false))
                        return "Each character must be a digit from [0-9] or an alphabetic character from A-F";
                }
            }
            
            return "Hex code is Valid";
        }
        
        public static void Main(string[] args)
        {
            Console.Write("Enter Hex code: ");
            string hex = Console.ReadLine();
            Console.WriteLine(Valid_hex(hex));
            
            Console.Write("Press any key to continue . . . ");
            Console.ReadKey(true);
        }
    }
}