using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        DateTime start_date = new DateTime(2017,9,28);

        DateTime end_date = new DateTime(2017,10,18);

        string[] no_months = Enumerable.Range(0, Int32.MaxValue).Select(e => start_date.AddMonths(e)).TakeWhile(e => e.Month <= end_date.Month).Select(e => e.ToString("yyyy_MM")).ToArray();

        foreach(string m in no_months)

        {

            Console.WriteLine(m);

        }

        List<string> list_mo = new List<string>();

        for (DateTime date = start_date; date.Month <= end_date.Month; date = date.AddMonths(1))

            list_mo.Add(date.ToString("yyyy_MM"));

        foreach(string m in list_mo.ToArray())

        {

            Console.WriteLine(m);

        }                   

    }

}