DateTimeHelper.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Framework / System / Windows / Controls / DateTimeHelper.cs / 1305600 / DateTimeHelper.cs
                        
                        
                            // (c) Copyright Microsoft Corporation. 
// This source is subject to [###LICENSE_NAME###].
// Please see [###LICENSE_LINK###] for details.
// All other rights reserved.
 
using System;
using System.Diagnostics; 
using System.Globalization; 

namespace System.Windows.Controls 
{
    // NOTICE: This date time helper assumes it is working in a Gregorian calendar
    //         If we ever support non Gregorian calendars this class would need to be redesigned
    internal static class DateTimeHelper 
    {
        private static System.Globalization.Calendar cal = new GregorianCalendar(); 
 
        public static DateTime? AddDays(DateTime time, int days)
        { 
            try
            {
                return cal.AddDays(time, days);
            } 
            catch (System.ArgumentException)
            { 
                return null; 
            }
        } 

        public static DateTime? AddMonths(DateTime time, int months)
        {
            try 
            {
                return cal.AddMonths(time, months); 
            } 
            catch (System.ArgumentException)
            { 
                return null;
            }
        }
 
        public static DateTime? AddYears(DateTime time, int years)
        { 
            try 
            {
                return cal.AddYears(time, years); 
            }
            catch (System.ArgumentException)
            {
                return null; 
            }
        } 
 
        public static DateTime? SetYear(DateTime date, int year)
        { 
            return DateTimeHelper.AddYears(date, year - date.Year);
        }

        public static DateTime? SetYearMonth(DateTime date, DateTime yearMonth) 
        {
            DateTime? target = SetYear(date, yearMonth.Year); 
            if (target.HasValue) 
            {
                target = DateTimeHelper.AddMonths(target.Value, yearMonth.Month - date.Month); 
            }

            return target;
        } 

        public static int CompareDays(DateTime dt1, DateTime dt2) 
        { 
            return DateTime.Compare(DiscardTime(dt1).Value, DiscardTime(dt2).Value);
        } 

        public static int CompareYearMonth(DateTime dt1, DateTime dt2)
        {
            return ((dt1.Year - dt2.Year) * 12) + (dt1.Month - dt2.Month); 
        }
 
        public static int DecadeOfDate(DateTime date) 
        {
            return date.Year - (date.Year % 10); 
        }

        public static DateTime DiscardDayTime(DateTime d)
        { 
            return new DateTime(d.Year, d.Month, 1, 0, 0, 0);
        } 
 
        public static DateTime? DiscardTime(DateTime? d)
        { 
            if (d == null)
            {
                return null;
            } 

            return d.Value.Date; 
        } 

        public static int EndOfDecade(DateTime date) 
        {
            return DecadeOfDate(date) + 9;
        }
 
        public static DateTimeFormatInfo GetCurrentDateFormat()
        { 
            return GetDateFormat(CultureInfo.CurrentCulture); 
        }
 
        internal static CultureInfo GetCulture(FrameworkElement element)
        {
            bool hasModifiers;
            CultureInfo culture; 
            if (element.GetValueSource(FrameworkElement.LanguageProperty, null, out hasModifiers) != BaseValueSourceInternal.Default)
            { 
                culture = MS.Internal.Text.DynamicPropertyReader.GetCultureInfo(element); 
            }
            else 
            {
                culture = CultureInfo.CurrentCulture;
            }
            return culture; 
        }
 
        internal static DateTimeFormatInfo GetDateFormat(CultureInfo culture) 
        {
            if (culture.Calendar is GregorianCalendar) 
            {
                return culture.DateTimeFormat;
            }
            else 
            {
                GregorianCalendar foundCal  =null; 
                DateTimeFormatInfo dtfi = null; 

                foreach (System.Globalization.Calendar cal in culture.OptionalCalendars) 
                {
                    if (cal is GregorianCalendar)
                    {
                        // Return the first Gregorian calendar with CalendarType == Localized 
                        // Otherwise return the first Gregorian calendar
                        if (foundCal == null) 
                        { 
                            foundCal = cal as GregorianCalendar;
                        } 

                        if (((GregorianCalendar)cal).CalendarType == GregorianCalendarTypes.Localized)
                        {
                            foundCal = cal as GregorianCalendar; 
                            break;
                        } 
                    } 
                }
 

                if (foundCal == null)
                {
                    // if there are no GregorianCalendars in the OptionalCalendars list, use the invariant dtfi 
                    dtfi = ((CultureInfo)CultureInfo.InvariantCulture.Clone()).DateTimeFormat;
                    dtfi.Calendar = new GregorianCalendar(); 
                } 
                else
                { 
                    dtfi = ((CultureInfo)culture.Clone()).DateTimeFormat;
                    dtfi.Calendar = foundCal;
                }
 
                return dtfi;
            } 
        } 

        // returns if the date is included in the range 
        public static bool InRange(DateTime date, CalendarDateRange range)
        {
            return InRange(date, range.Start, range.End);
        } 

        // returns if the date is included in the range 
        public static bool InRange(DateTime date, DateTime start, DateTime end) 
        {
            Debug.Assert(DateTime.Compare(start, end) < 1); 

            if (CompareDays(date, start) > -1 && CompareDays(date, end) < 1)
            {
                return true; 
            }
 
            return false; 
        }
 


        public static string ToDayString(DateTime? date, CultureInfo culture)
        { 
            string result = string.Empty;
            DateTimeFormatInfo format = GetDateFormat(culture); 
 
            if (date.HasValue && format != null)
            { 
                result = date.Value.Day.ToString(format);
            }

            return result; 
        }
 
        // This is specifically for Calendar.  It switches which year is at the beginning or end of the string. 
        public static string ToDecadeRangeString(int decade, FrameworkElement fe)
        { 
            string result = string.Empty;
            DateTimeFormatInfo format = DateTimeHelper.GetDateFormat(DateTimeHelper.GetCulture(fe));

            if (format != null) 
            {
                bool isRightToLeft = fe.FlowDirection==FlowDirection.RightToLeft; 
                int decadeRight = isRightToLeft?decade:(decade+9); 
                int decadeLeft =  isRightToLeft?(decade+9):decade;
                result = decadeLeft.ToString(format) + "-" + decadeRight.ToString(format); 
            }

            return result;
        } 

        public static string ToYearMonthPatternString(DateTime? date, CultureInfo culture) 
        { 
            string result = string.Empty;
            DateTimeFormatInfo format = GetDateFormat(culture); 

            if (date.HasValue && format != null)
            {
                result = date.Value.ToString(format.YearMonthPattern, format); 
            }
 
            return result; 
        }
 
        public static string ToYearString(DateTime? date, CultureInfo culture)
        {
            string result = string.Empty;
            DateTimeFormatInfo format = GetDateFormat(culture); 

            if (date.HasValue && format != null) 
            { 
                result = date.Value.Year.ToString(format);
            } 

            return result;
        }
 
        public static string ToAbbreviatedMonthString( DateTime? date, CultureInfo culture)
        { 
            string result = string.Empty; 
            DateTimeFormatInfo format = GetDateFormat(culture);
 
            if (date.HasValue && format != null)
            {
                string[] monthNames = format.AbbreviatedMonthNames;
                if (monthNames != null && monthNames.Length > 0) 
                {
                    result = monthNames[(date.Value.Month - 1) % monthNames.Length]; 
                } 
            }
 
            return result;
        }

        public static string ToLongDateString(DateTime? date, CultureInfo culture) 
        {
            string result = string.Empty; 
            DateTimeFormatInfo format = GetDateFormat(culture); 

            if (date.HasValue && format != null) 
            {
                result = date.Value.Date.ToString(format.LongDatePattern, format);
            }
 
            return result;
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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DateTimeHelper.cs source code in C# .NET

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