project euler 17, C#, C#

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//Title of this code
//Rextester.Program.Main is the entry point for your code. Don't change it.

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

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            int sum = 0;
            for(int i=1; i<1000; i++)
                sum += GetNumberInWords(i.ToString()).Replace(" ", "").Trim().Count();
            Console.WriteLine(sum+"onethousand".Count());
        }
        
        public static string GetNumberInWords(string n)
        {
            if (string.IsNullOrEmpty(n))
                return "";

int number = Convert.ToInt32(n);
            if(number == 0)
                return "zero";
            
            int type = 0;
            int remainder = number;
            string res = "";
            if (number % 100 > 9 && number % 100 < 20)
            {
                res = GetPartInWords(number % 100, 1);
                type = 2;
                remainder = number / 100;
            }
            while (remainder != 0)
            { 
                type++;
                int factor = 10;
                if(type >= 4)
                    factor = 1000;
                res = GetPartInWords(remainder % factor, type).Trim() + " " + res.Trim();
                remainder = remainder / factor;
            }
            
            string[] parts = res.Split(" ".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
            
            if(parts.Count() == 3)
                return string.Format("{0} {1} and {2}", parts[0], parts[1], parts[2]);
            if(parts.Count() == 4)
                return string.Format("{0} {1} and {2} {3}", parts[0], parts[1], parts[2], parts[3]);
            
                
            return res;
        }
        static string GetPartInWords(int number, int type)
        {
            if (type == 1) //0-19
            {
                switch (number)
                { 
                    case 1:
                        return "one";
                    case 2:
                        return "two";
                    case 3:
                        return "three";
                    case 4:
                        return "four";
                    case 5:
                        return "five";
                    case 6:
                        return "six";
                    case 7:
                        return "seven";
                    case 8:
                        return "eight";
                    case 9:
                        return "nine";
                    case 10:
                        return "ten";
                    case 11:
                        return "eleven";
                    case 12:
                        return "twelve";
                    case 13:
                        return "thirteen";
                    case 14:
                        return "fourteen";
                    case 15:
                        return "fifteen";
                    case 16:
                        return "sixteen";
                    case 17:
                        return "seventeen";
                    case 18:
                        return "eighteen";
                    case 19:
                        return "nineteen";
                }
            }
            if (type == 2)  //20,30,40,50,60,70,80,90
            {
                switch (number)
                { 
                    case 2:
                        return "twenty";
                    case 3:
                        return "thirty";
                    case 4:
                        return "forty";
                    case 5:
                        return "fifty";
                    case 6:
                        return "sixty";
                    case 7:
                        return "seventy";
                    case 8:
                        return "eighty";
                    case 9:
                        return "ninety";
                }
            }
            if (type == 3) //100, 200, 300, 400, 500, 600, 700, 800, 900
            {
                switch (number)
                { 
                    case 1:
                        return "one hundred";
                    case 2:
                        return "two hundred";
                    case 3:
                        return "three hundred";
                    case 4:
                        return "four hundred";
                    case 5:
                        return "five hundred";
                    case 6:
                        return "six hundred";
                    case 7:
                        return "seven hundred";
                    case 8:
                        return "eight hundred";
                    case 9:
                        return "nine hundred";
                }
            }            
            return "";
        }
    }
}

Show compiler warnings [ + ] Show input
Compilation time: 0.45 sec, absolute running time: 0.17 sec, cpu time: 0.11 sec, average memory usage: 24 Mb, average nr of threads: 5