using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        int i = 554;

        string str = ToString(i);

        Console.WriteLine(str);

    }

    static IEnumerable<char> ToChar(int num)

    {

        while (num > 0)

        {

            char ch = (char)((num % 10) + '0');

            num /= 10;

            yield return ch;

        }

    }

    // Without yield

    static char[] ToCharSimplified(int num)

    {

        char[] result = new char[64];

        int count = 0;

        while (num > 0)

        {

            char ch = (char)((num % 10) + '0');

            result[count++] = ch;

            num /= 10;

        }

        return result;

    }

​

    static string ToString(int num)

    {

        var chArray = ToCharSimplified(num).Reverse().ToArray();

        string str = new string(chArray);

        return str;

    }

}

​

​