using System;

using Microsoft.Xrm.Sdk;

public class Program

{

    public static void Main()

    {

        var date = new DateTime(2021, 8, 15);

        print(date, "startdato");

        print(GetFirstDate(date, 1), "månedlig");

        print(GetFirstDate(date, 2), "kvartal");

        print(GetFirstDate(date, 3), "halvårlig");

        print(GetFirstDate(date, 4), "årlig");

        date = new DateTime(2021, 12, 15);

        print(date, "startdato");

        print(GetFirstDate(date, 1), "månedlig");

        print(GetFirstDate(date, 2), "kvartal");

        print(GetFirstDate(date, 3), "halvårlig");

        print(GetFirstDate(date, 4), "årlig");

        Decimal pris = 6240;

        // bergn pris

        DateTime fromDate   = new DateTime(2021,08,04);

        DateTime toDate     = new DateTime(2021,08,05);

        var antall = GetCalculationFraction(toDate, fromDate);

        printStr("Antall:"+antall.ToString());

        var belop =  pris * antall;

        printStr(belop.ToString());

        printStr(pris.ToString());

    }

​

​

private static decimal GetCalculationFraction(DateTime ToDate, DateTime FromDate)

        {

            double numberOfYearsInMonths = (ToDate.Year - FromDate.Year) * 12;

            double numberOfMonths = (ToDate.Month - FromDate.Month);

            var totalMonths = numberOfYearsInMonths + numberOfMonths;

printStr(totalMonths.ToString());

            if (ToDate.Day != FromDate.Day)

            {

                var month = FromDate.Month;

                var days = 0;

                switch (month)

                {

                    case 2:

                        days = 28;

                        break;

                    case 4:

                        days = 30;

                        break;

                    case 6:

                        days = 30;

                        break;

                    case 9:

                        days = 30;

                        break;

                    case 11:

                        days = 30;

                        break;

                    default:

                        days = 31;

                        break;

                }

               var  numberOfDays = days - FromDate.Day + ToDate.Day;

printStr("days"+days.ToString());                               

printStr("numberofdays"+numberOfDays.ToString());               

               totalMonths += (numberOfDays / days);

printStr(totalMonths.ToString());       

                printStr((totalMonths/12).ToString());      

            }

​

            return (decimal)(totalMonths / 12);

        }   

    public static DateTime GetFirstDate(DateTime date, int frequency)

    {

        const int MONTH = 1;

        const int QUARTER = 2;

        const int HALFYEAR = 3;

        const int YEAR = 4;

        switch (frequency)

        {

            case MONTH:

                return date.Day >= 20 ? new DateTime(date.Year, date.Month + 1, 1) : new DateTime(date.Year, date.Month, 1);

            case QUARTER:

                return date.GetNextQuarterStart();

            case HALFYEAR:

                return date.GetNextHalfYearStart();

            case YEAR:

                return date.GetNextYearStart();

            default:

                return date;

        }

    }

    /*public static DateTime GetLastDate(DateTime date, int frequency)

    {

        const int MONTH = 1;

        const int QUARTER = 2;

        const int HALFYEAR = 3;

        const int YEAR = 4;

        switch (frequency)

        {

            case MONTH:

                return date.Day >= 20 ? new DateTime(date.Year, date.Month + 1, 1) : new DateTime(date.Year, date.Month, 1);

            case QUARTER:

                return date.GetNextQuarterEnd();

            case HALFYEAR:

                return date.GetNextHalfYearEnd();

            case YEAR:

                return date.GetNextYearEnd();

            default:

                return date;

        }

    }*/

    public static void print(DateTime d, string s)

    {

        Console.WriteLine(d.ToString("dd.MM.yyyy") + (s != null ? " : " + s : ""));

    }

    public static void printStr(string s)

    {

        Console.WriteLine(s);

    }   

}

​

public static class DateTimeExtensions

{

        public static int GetQuarterStart(this DateTime date)

    {

        return (date.Month + 2) / 3;

    }

​

    public static DateTime GetNextQuarterStart(this DateTime date)

    {

        int firstMndInQuarter = (((date.Month + 2) / 3) * 3) + 1 > 10 ? 1 : (((date.Month + 2) / 3) * 3) + 1;

        int year = firstMndInQuarter == 1 ? date.Year + 1 : date.Year;

        return new DateTime(year, firstMndInQuarter, 1);

    }

​

    public static DateTime GetNextHalfYearStart(this DateTime date)

    {

        return date.Month < 7 ? new DateTime(date.Year, 7, 1) : new DateTime(date.Year + 1, 1, 1);

    }

​

    public static DateTime GetNextYearStart(this DateTime date)

    {

        return new DateTime(date.Year + 1, 1, 1);

    }

}

    /*

    public static int GetQuarterStart(this DateTime date)

    {

        return (date.Month + 2) / 3;

    }

​

    public static DateTime GetNextQuarterStart(this DateTime date)

    {

        int firstMndInQuarter = (((date.Month + 2) / 3) * 3) + 1 > 10 ? 1 : (((date.Month + 2) / 3) * 3) + 1;

        int year = firstMndInQuarter == 1 ? date.Year + 1 : date.Year;

        return new DateTime(year, firstMndInQuarter, 1);

    }

​

    public static DateTime GetNextHalfYearStart(this DateTime date)

    {

        return date.Month < 7 ? new DateTime(date.Year, 7, 1) : new DateTime(date.Year + 1, 1, 1);

    }

​

    public static DateTime GetNextYearStart(this DateTime date)

    {

        return new DateTime(date.Year + 1, 1, 1);

    }

    */

​