For Reddit Easy Challenge 287

Kaprekars_Routine.cs

using System;
using System.Linq;

namespace Kaprekars_Routine
{
    class Program
    {
        const int KAPREKAR_CONSTANT = 6174;

        static void Main(string[] args)
        {
            string input = Console.ReadLine();

            Validate(input);

            while(input.Length < 4)
                input += "0";

            Console.WriteLine(LargestDigit(input));
            Console.WriteLine(DescDigits(input));
            Console.WriteLine(Kaprekars(input));

            Console.ReadKey();
        }

        /// <summary>
        /// Returns the largest digit from the passed in string
        /// </summary>
        static int LargestDigit(string input)
        {
            return (int)Char.GetNumericValue(
                input.ToArray()
                .OrderByDescending(x => x)
                .Take(1).Single());
        }

        /// <summary>
        /// Returns the digits in descending order
        /// </summary>
        static int DescDigits(string input)
        {
            return Convert.ToInt16(
                new string(input
                    .ToArray()
                    .OrderByDescending(x => x)
                    .ToArray()));
        }

        /// <summary>
        /// Returns the digits in ascending order
        /// </summary>
        static int AscDigits(string input)
        {
            return Convert.ToInt16(
                new string(input
                    .ToArray()
                    .OrderBy(x => x)
                    .ToArray()));
        }

        /// <summary>
        /// Validates the input
        /// </summary>
        static void Validate(string input)
        {
            if (input.Length > 4 || input.ToArray().Distinct().Count() < 2)
                throw new Exception("Invalid Input");
        }

        /// <summary>
        /// Determines how long it'll take to get to Kaprekar's Constant
        /// </summary>
        static int Kaprekars(string input)
        {
            int counter = 0,
                test = Convert.ToInt16(input);

            while(test != KAPREKAR_CONSTANT)
            {
                test = DescDigits(test.ToString()) - AscDigits(test.ToString());
                counter++;

                while (test.ToString().Length < 4)
                    test = Convert.ToInt16(test.ToString() + "0");
            }

            return counter;
        }
    }
}

For reddit easy challenge #287