Numeral System 1 option 2

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

namespace _01.DecimalToBinary
{
    class DecimalToBinary
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Enter decimal number: ");
            int enteredNumber = int.Parse(Console.ReadLine());

            //generate random number
            //Random randomNumber = new Random();
            //int enteredNumber = randomNumber.Next(-10000000, 10000000);

            Console.WriteLine(enteredNumber);
            string binaryNumber = ConvertToBinary(enteredNumber);
            Console.WriteLine(binaryNumber);

        }

        private static string ConvertToBinary(int enteredNumber)
        {
            int length = Convert.ToString(enteredNumber, 2).Length;
            int mask;
            int result;
            StringBuilder binary = new StringBuilder();
            for (int i = length-1; i >=0; i--)
            {   //we start from the last bit otherwise
                //we have to reverse the binary array at the end
                //this is because of the Append method
                mask = 1<<i;
                result = (enteredNumber & mask) >> i; //check 1 or 0
                binary.Append(result);
            }

            return binary.ToString();
        }
    }
}