using System;

public class Program

{

    public static void Main()

    {

        Program p = new Program();

        DateTime CoverStartDate = Convert.ToDateTime("2021-08-10 00:00:00.000"); // CoverStartDate

        DateTime CancellationDate = Convert.ToDateTime("2022-02-12 23:59:59.000"); // CancellationDate

        int answer = p.GetConsumerMonthsElapsed(CoverStartDate, CancellationDate);

        //Console.WriteLine("Difference is " + (CoverStartDate.Month - CancellationDate.Month));

        Console.WriteLine("Cover Start Date = " + CoverStartDate);

        Console.WriteLine();

        Console.WriteLine("Cancellation Date = " + CancellationDate);

        Console.WriteLine();

        Console.WriteLine("Consumer Months Elapsed = " + answer);

    }

    public int GetConsumerMonthsElapsed(DateTime coverStartDate, DateTime CancellationDate)

    {

            int consumerMonthsElapsed = 0;

​

            DateTime coverStartDateTimeForLoop = coverStartDate;

            //for (int month = 0; month <= DateAndTime.DateDiff(DateInterval.Month, startDate, cutOffDateTime); month++)

            for (int month = 0; month <= (coverStartDate.Month - CancellationDate.Month); month++)

            {

                if (coverStartDateTimeForLoop <= CancellationDate)

                {

                    consumerMonthsElapsed++;

                    coverStartDateTimeForLoop = coverStartDate.AddMonths(month + 1);

                    //coverStartDateTimeForLoop = DateAndTime.DateAdd(DateInterval.Month, month + 1, startDate);

                }

            }

​

            return consumerMonthsElapsed;

    }

}