C#-Code

using System;

namespace ConsoleGrayCode
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("--- Gray-Code ---");
            uint i;
            bool loop = true;
            do
            {
                Console.Write("Geben Sie eine positive Zahl ein: ");
                loop = uint.TryParse(Console.ReadLine(), out i);
                string grayCode;
                uint transform;
                if (loop)
                {
                    grayCode = ToGrayCode(i);
                    transform = FromGrayCode(grayCode);
                    Console.WriteLine("Gray-Code: {0} \tRücktransformiert: {1}", grayCode, transform);
                }
                else
                {
                    Console.WriteLine("Bitte nur positive Zahlen eingeben.\nDas Programm wird beendet.");
                }
            }
            while (loop);

            Console.ReadKey();
        }

        static string ToGrayCode(uint i)
        {
            return Convert.ToString((i >> 1) ^ i, 2);
        }

        static uint FromGrayCode(string code)
        {
            uint v = Convert.ToUInt32(code, 2);

            int index = code.IndexOf('1');
            if (index == -1)
            { return 0; }
            int l = 4;
            for (int i = l; i >= 0; i--)
            {
                v = v ^ (v >> (int)Math.Pow(2, i));
            }

            return v;
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GrayCode
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Welche Zahl soll als GrayCode ausgegeben werden?");
            int Number = Convert.ToInt32(Console.ReadLine());
            Converter Hex = new Converter();
            int Size = 1;
            Hex.CheckSize(Number, ref Size);
            int[] resultHex = new int[Size];
            string[] resultGray = new string[Size];
            Hex.ConvertingToHex(Number, ref resultHex);
            Hex.ConvertingToGray(resultHex, ref resultGray);
            Console.WriteLine("GrayCode:");
            for(int i = 1; i < Size+1; i++)
            {
                Console.WriteLine(resultGray[Size - i]);
            }
            Console.ReadLine();
        }
    }
    class Converter
    {
        public void CheckSize(int Num, ref int Size)
        {
            while (Num > 1)
            {

                if (Num <= 15)
                {
                    Num = 0;
                }
                else
                {
                    Size++;
                    Num = Num / 16;
                }
            }
        }
        public void ConvertingToHex(int Num, ref int[] Numbers)
        {
            int j = 0;
            while (Num > 1)
            {
                
                if (Num <= 15)
                {
                    Numbers[j] = Num;
                    Num = 0;
                }
                else
                {
                Numbers[j] = Num%16;
                Num = Num / 16;
                j++;
                }
            }
        }
        public void ConvertingToGray(int[] Numbers, ref string[] result)
        {
            int lauf = 0;
            foreach(int k in Numbers)
            {
                switch(k)
                {
                    case 0: result[lauf] = "0000"; break;
                    case 1: result[lauf] = "0001"; break;
                    case 2: result[lauf] = "0011"; break;
                    case 3: result[lauf] = "0010"; break;
                    case 4: result[lauf] = "0110"; break;
                    case 5: result[lauf] = "0111"; break;
                    case 6: result[lauf] = "0101"; break;
                    case 7: result[lauf] = "0100"; break;
                    case 8: result[lauf] = "1100"; break;
                    case 9: result[lauf] = "1101"; break;
                    case 10: result[lauf] = "1111"; break;
                    case 11: result[lauf] = "1110"; break;
                    case 12: result[lauf] = "1010"; break;
                    case 13: result[lauf] = "1011"; break;
                    case 14: result[lauf] = "1001"; break;
                    case 15: result[lauf] = "1000"; break;
                }
                lauf++;
            }
        }
    }
}

C#-Code

using System;
using static System.Console;

namespace gray_code { 

    class Program    {

        static string NL = Environment.NewLine;
        static void Main()        {

            bool bo_exit = false;
            while (!bo_exit)            {
                uint input = 0;

                bool bo_input_ok = false;
                while (!bo_input_ok)                {
                    string sinput = (NL + "give me an uint for gray coding: ").Message();
                    bo_input_ok = uint.TryParse(sinput, out input);
                }

                WriteLine("gray  : " + BinaryToGray(input).Convert());
                WriteLine("binary: " + input.GetBinaryString());
                
                ConsoleKeyInfo ki ="again? exit with ESC".EndMessage();
                bo_exit = ki.Key == ConsoleKey.Escape;
            }
        }

        static uint BinaryToGray(uint num)        {
            return (num >> 1) ^ num;
        }
    }

    public static class MyExtensions    {

        public static ConsoleKeyInfo EndMessage(this string s)        {
            Write(s); return ReadKey(true);
        }

        public static string Message(this string s)        {
            Write(s); return ReadLine();
        }

        public static string Convert(this uint x)        {

            char[] bits = new char[32];
            int i = 0;

            while (x != 0)            {
                bits[i++] = (x & 1) == 1 ? '1' : '0';
                x >>= 1;
            }

            Array.Reverse(bits, 0, i);
            return new string(bits);
        }

        // Convert Integer to binary and return as string
        public static string GetBinaryString(this uint n)
        {
            char[] b = new char[sizeof(Int32) * 8];

            for (int i = 0; i < b.Length; i++)
                b[b.Length - 1 - i] = ((n & (1 << i)) != 0) ? '1' : '0';

            return new string(b).TrimStart('0');
        }
    }
}