unfinished

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

class NumeralSystemConversions
{
    static void Main()
    {
        while (true)
        {
            Console.WriteLine(@"{1} Convert Decimal to Binary.
{2} Convert Decimal to Hexadecimal.
{3} Convert Binary  to Decimal.
{4} Convert Binary  to Hexadecimal.
{5} Convert Hexadecimal to Decimal.
{6} Convert Hexadecimal to Binary.
{9} Exit." + "\r\n");

            string input = Console.ReadLine();
            int answer;
            bool checkInput = int.TryParse(input, out answer);

            if (answer == 1)
            {
                                                    //Convert 1234d to binary
                Console.Write("Decimal:  ");
                string inputDB = Console.ReadLine();
                int decimBin;
                bool checkinputDB = int.TryParse(inputDB, out decimBin);

                string binN = "";

                while (decimBin > 0)
                {
                    int residue = decimBin % 2;
                    decimBin /= 2;
                    binN = residue + binN;
                }

                Console.WriteLine("\r\nBinary Result:");
                Console.WriteLine("{0}", binN.PadLeft(16, '0'));
                Console.WriteLine("{0}", binN);
            }

            else if (answer == 2)
            {
                                        //  Convert 1234d to hexadecimal
                Console.Write("Decimal:  ");
                string inputDB = Console.ReadLine();
                int decimHex;
                bool checkinputDB = int.TryParse(inputDB, out decimHex);

                string hexN = "";

                while (decimHex > 0)
                {
                    int residue = decimHex % 16;
                    decimHex /= 16;
                    switch (residue)
                    {
                        case 10: hexN = 'A' + hexN; break;
                        case 11: hexN = 'B' + hexN; break;
                        case 12: hexN = 'C' + hexN; break;
                        case 13: hexN = 'D' + hexN; break;
                        case 14: hexN = 'E' + hexN; break;
                        case 15: hexN = 'F' + hexN; break;
                        default: hexN = residue + hexN; break;
                    }
                }
                Console.WriteLine("\r\nHexadecimal Result:");
                Console.WriteLine(hexN);
            }

            else if (answer == 3)
            {
                //// Convert 1100101b to decimal        ------------
                string binD = "1100101";
                int count = 0;
                int pow = binD.Length - 1;
                double decimNumb = 0;

                foreach (var item in binD)
                {
                    decimNumb += Math.Pow(((int)item % 2) * 2, pow - count);
                    count++;
                }
                Console.WriteLine(decimNumb);
            }
            else if (answer == 4)
            {
                // Convert 1100101b to hexadecimal      ------------
                string binH = "1100101";
                string strHex = Convert.ToInt32(binH, 2).ToString("X");
                Console.WriteLine(strHex);
            }
            else if (answer == 5)
            {
                ////Convert ABChex to decimal
                string hexD = "A0A";
                int count = (hexD.Length - 1);
                double deciSum = 0;
                foreach (var item in hexD)
                {
                    switch (item)
                    {
                        case '1': deciSum += 1 * Math.Pow(16, count); break;
                        case '2': deciSum += 2 * Math.Pow(16, count); break;
                        case '3': deciSum += 3 * Math.Pow(16, count); break;
                        case '4': deciSum += 4 * Math.Pow(16, count); break;
                        case '5': deciSum += 5 * Math.Pow(16, count); break;
                        case '6': deciSum += 6 * Math.Pow(16, count); break;
                        case '7': deciSum += 7 * Math.Pow(16, count); break;
                        case '8': deciSum += 8 * Math.Pow(16, count); break;
                        case '9': deciSum += 9 * Math.Pow(16, count); break;
                        case 'A': deciSum += 10 * Math.Pow(16, count); break;
                        case 'B': deciSum += 11 * Math.Pow(16, count); break;
                        case 'C': deciSum += 12 * Math.Pow(16, count); break;
                        case 'D': deciSum += 13 * Math.Pow(16, count); break;
                        case 'E': deciSum += 14 * Math.Pow(16, count); break;
                        case 'F': deciSum += 15 * Math.Pow(16, count); break;
                    }
                    count--;
                }
                Console.WriteLine(deciSum);

            }
            else if (answer == 6)
            {
                //Convert ABChex to binary
                string hexB = "FFFF";
                int count = (hexB.Length - 1);
                string binSum = "";

                foreach (var item in hexB)
                {
                    switch (item)
                    {
                        case '0': binSum = "0000"; break;
                        case '1': binSum = "0001"; break;
                        case '2': binSum = "0010"; break;
                        case '3': binSum = "0011"; break;
                        case '4': binSum = "0100"; break;
                        case '5': binSum = "0101"; break;
                        case '6': binSum = "0110"; break;
                        case '7': binSum = "0111"; break;
                        case '8': binSum = "1000"; break;
                        case '9': binSum = "1001"; break;
                        case 'A': binSum = "1010"; break;
                        case 'B': binSum = "1011"; break;
                        case 'C': binSum = "1100"; break;
                        case 'D': binSum = "1101"; break;
                        case 'E': binSum = "1110"; break;
                        case 'F': binSum = "1111"; break;
                    }
                    Console.Write(binSum);
                    Console.Write(" ");
                }
                Console.WriteLine();
                //Console.WriteLine(binSum);
            }

            else if (answer == 9)
            {
                return;
            }
            Console.ReadKey();
            Console.Clear();
        }
    }
}

/*
    Convert 1234d to binary and hexadecimal numeral systems.
    Convert 1100101b to decimal and hexadecimal numeral systems.
    Convert ABChex to decimal and binary numeral systems.

 */