all about hijri calendar D365

using Microsoft.Dynamics.ApplicationPlatform.Environment;
using Microsoft.Dynamics.ApplicationPlatform.Environment.Settings;
using System;
using System.Globalization;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading;

public static class ALM_Global
{ 

    public static str startDateHijri(str _date)
    {
        int d,m,y;
        TransDate dt,dt1;
        str finalDate;
        str hijriDate = _date;
        dt = str2Date(hijriDate,213);
        d = dayOfMth(dt);
        m = mthofyr(dt);
        y = year(dt);
        var hdate = new DateTime(y,m, 1);
       
        finalDate = hdate.ToString("MM/dd/yyyy");
        return finalDate;
    }

    public static str endDateHijri(str _date)
    {
        int days,d,m,y;
        TransDate dt,dt1;
        str finalDate;
        str hijriDate = _date;

        dt = str2Date(hijriDate,213);
        d = dayOfMth(dt);
        m = mthofyr(dt);
        y = year(dt);

        UmAlQuraCalendar cal = new UmAlQuraCalendar();
        days = cal.GetDaysInMonth(y, m);
       // var hdate = new DateTime(y,m, days);
        finalDate = int2Str(m)+'/'+int2Str(days)+'/'+int2Str(y);
       // finalDate = hdate.ToString("MM/dd/yyyy");
        return finalDate;
    }

    public static str hijriToGregorian(str _hijriDate)
    {
        System.Globalization.CultureInfo arCul = new System.Globalization.CultureInfo("ar-SA");
        System.Globalization.CultureInfo enCul = new System.Globalization.CultureInfo("en-US");
        System.DateTime tempDateTime;
        str strTemp,finalDate,hDate,hmonth,hYear;
        System.String[] arr;
        date grDate;
        str hijriDate;
        ;
        //grDate = str2Date(_hijriDate,123);
        //hDate = date2Str(_hijriDate,123,DateDay::Digits2,DateSeparator::Slash,DateMonth::Digits2,DateSeparator::Slash,DateYear::Digits4);
        //all expected dates formats
        arr = new System.String[4]();
       
        arr.SetValue("dd/MM/yyyy", 0);
        arr.SetValue("M/dd/yyyy" , 1);
        arr.SetValue("M/d/yyyy"  , 2);
        arr.SetValue("MM/dd/yyyy", 3);
       
        if(_hijriDate != '')
        {
            tempDateTime = System.DateTime::ParseExact(_hijriDate, arr, arCul, System.Globalization.DateTimeStyles::AllowWhiteSpaces);
            strTemp = tempDateTime.ToString("MM/dd/yyyy");
            //grDate = str2date(strTemp, 123);
            finalDate = strTemp;
        }
        return finalDate;
    }

    public static str getMonthHijri(TransDate date, int periods)
    {
        str hDate,hmonth,hYear,finalDate;
        int gDate,gMonth,gYear;
        ;
        gDate  = dayOfMth(_date);
        gMonth = mthOfYr(_date);
        gYear  = year(_date);

        // Sets a DateTime of the Gregorian calendar.
        DateTime myDT = new DateTime(gYear,gMonth,gDate, new GregorianCalendar());
     
        // Creates an instance of the HijriCalendar.
        HijriCalendar myCal = new HijriCalendar();
       
        myDT     = myCal.AddMonths( myDT, _periods );
        hDate    = int2Str(myCal.GetDayOfMonth(myDT));
        hmonth   = int2Str(myCal.GetMonth(myDT));
        hYear    = int2Str(myCal.GetYear(myDT));
        finalDate = hmonth+"/"+hdate+"/"+hYear;
        return finalDate;

    }

    public static str getNextMonthHijri(str date, int periods)
    {
        str hDate,hmonth,hYear,finalDate,hijriDate, dt1,dt2;
        int gDate,gDate1,gMonth,gYear;
        ;
        dt1 = strDel(_date,1,3);
        //info(a);
        dt2 = strDel(dt1,3,5);

        //Info(b);
        gDate  = str2Int(dt2);
        gMonth = str2Int(strDel(_date,3,8));
        gYear  = str2Int(strDel(_date,1,6));

        //// Sets a DateTime of the Gregorian calendar.
        DateTime myDT = new DateTime(gYear,gMonth,gDate, new HijriCalendar());
     
        // Creates an instance of the HijriCalendar.
        HijriCalendar myCal = new HijriCalendar();
       
        myDT     = myCal.AddMonths( myDT, _periods );
        hDate    = int2Str(myCal.GetDayOfMonth(myDT));
        hmonth   = int2Str(myCal.GetMonth(myDT));
        hYear    = int2Str(myCal.GetYear(myDT));
        finalDate = hmonth+"/"+hdate+"/"+hYear;
        return finalDate;

    }

    public static str getNextWeekHijri(str date, int periods)
    {
        str hDate,hmonth,hYear,finalDate,hijriDate, dt1,dt2;
        int gDate,gDate1,gMonth,gYear;
        ;
        dt1 = strDel(_date,1,3);
        //info(a);
        dt2 = strDel(dt1,3,5);

        //Info(b);
        gDate  = str2Int(dt2);
        gMonth = str2Int(strDel(_date,3,8));
        gYear  = str2Int(strDel(_date,1,6));

        //// Sets a DateTime of the Gregorian calendar.
        DateTime myDT = new DateTime(gYear,gMonth,gDate, new HijriCalendar());
     
        // Creates an instance of the HijriCalendar.
        HijriCalendar myCal = new HijriCalendar();
       
        myDT     = myCal.AddWeeks( myDT, _periods );
        hDate    = int2Str(myCal.GetDayOfMonth(myDT));
        hmonth   = int2Str(myCal.GetMonth(myDT));
        hYear    = int2Str(myCal.GetYear(myDT));
        finalDate = hmonth+"/"+hdate+"/"+hYear;
        return finalDate;

    }

    public static str getHijriDate(TransDate _date)
    {
        int gDate,gMonth,gYear;
        gDate  = dayOfMth(_date);
        gMonth = mthOfYr(_date);
        gYear  = year(_date);
     

        System.Globalization.CultureInfo arCul = new System.Globalization.CultureInfo("ar-SA");
        DateTime dt = new DateTime(gYear, gMonth, gDate);
        str s = dt.ToString("M/dd/yyyy", arCul);
        //MessageBox.Show(s);
        return s;
    }

}