private TimeZoneInfo(Win32Native.TimeZoneInformation zone, bool dstDisabled)
{
if (string.IsNullOrEmpty(zone.StandardName))
{
_id = LocalId; // the ID must contain at least 1 character - initialize _id to "Local"
}
else
{
_id = zone.StandardName;
}
_baseUtcOffset = new TimeSpan(0, -(zone.Bias), 0);
if (!dstDisabled)
{
// only create the adjustment rule if DST is enabled
Win32Native.RegistryTimeZoneInformation regZone = new Win32Native.RegistryTimeZoneInformation(zone);
AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(regZone, DateTime.MinValue.Date, DateTime.MaxValue.Date, zone.Bias);
if (rule != null)
{
_adjustmentRules = new AdjustmentRule[1];
_adjustmentRules[0] = rule;
}
}
ValidateTimeZoneInfo(_id, _baseUtcOffset, _adjustmentRules, out _supportsDaylightSavingTime);
_displayName = zone.StandardName;
_standardDisplayName = zone.StandardName;
_daylightDisplayName = zone.DaylightName;
}
/// <summary>
/// Helper function that compares a TimeZoneInformation struct to a time zone registry entry.
/// </summary>
private static bool TryCompareTimeZoneInformationToRegistry(Win32Native.TimeZoneInformation timeZone, string id, out bool dstDisabled)
{
dstDisabled = false;
using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id, writable: false))
{
if (key == null)
{
return(false);
}
Win32Native.RegistryTimeZoneInformation registryTimeZoneInfo;
byte[] regValue = key.GetValue(TimeZoneInfoValue, null, RegistryValueOptions.None) as byte[];
if (regValue == null || regValue.Length != RegByteLength)
{
return(false);
}
registryTimeZoneInfo = new Win32Native.RegistryTimeZoneInformation(regValue);
//
// first compare the bias and standard date information between the data from the Win32 API
// and the data from the registry...
//
bool result = TryCompareStandardDate(timeZone, registryTimeZoneInfo);
if (!result)
{
return(false);
}
result = dstDisabled || CheckDaylightSavingTimeNotSupported(timeZone) ||
//
// since Daylight Saving Time is not "disabled", do a straight comparision between
// the Win32 API data and the registry data ...
//
(timeZone.DaylightBias == registryTimeZoneInfo.DaylightBias &&
timeZone.DaylightDate.Year == registryTimeZoneInfo.DaylightDate.Year &&
timeZone.DaylightDate.Month == registryTimeZoneInfo.DaylightDate.Month &&
timeZone.DaylightDate.DayOfWeek == registryTimeZoneInfo.DaylightDate.DayOfWeek &&
timeZone.DaylightDate.Day == registryTimeZoneInfo.DaylightDate.Day &&
timeZone.DaylightDate.Hour == registryTimeZoneInfo.DaylightDate.Hour &&
timeZone.DaylightDate.Minute == registryTimeZoneInfo.DaylightDate.Minute &&
timeZone.DaylightDate.Second == registryTimeZoneInfo.DaylightDate.Second &&
timeZone.DaylightDate.Milliseconds == registryTimeZoneInfo.DaylightDate.Milliseconds);
// Finally compare the "StandardName" string value...
//
// we do not compare "DaylightName" as this TimeZoneInformation field may contain
// either "StandardName" or "DaylightName" depending on the time of year and current machine settings
//
if (result)
{
string registryStandardName = key.GetValue(StandardValue, string.Empty, RegistryValueOptions.None) as string;
result = string.Equals(registryStandardName, timeZone.StandardName, StringComparison.Ordinal);
}
return(result);
}
}
/// <summary>
/// Converts a Win32Native.RegistryTimeZoneInformation (REG_TZI_FORMAT struct) to an AdjustmentRule.
/// </summary>
private static AdjustmentRule CreateAdjustmentRuleFromTimeZoneInformation(Win32Native.RegistryTimeZoneInformation timeZoneInformation, DateTime startDate, DateTime endDate, int defaultBaseUtcOffset)
{
bool supportsDst = timeZoneInformation.StandardDate.Month != 0;
if (!supportsDst)
{
if (timeZoneInformation.Bias == defaultBaseUtcOffset)
{
// this rule will not contain any information to be used to adjust dates. just ignore it
return(null);
}
return(AdjustmentRule.CreateAdjustmentRule(
startDate,
endDate,
TimeSpan.Zero, // no daylight saving transition
TransitionTime.CreateFixedDateRule(DateTime.MinValue, 1, 1),
TransitionTime.CreateFixedDateRule(DateTime.MinValue.AddMilliseconds(1), 1, 1),
new TimeSpan(0, defaultBaseUtcOffset - timeZoneInformation.Bias, 0), // Bias delta is all what we need from this rule
noDaylightTransitions: false));
}
//
// Create an AdjustmentRule with TransitionTime objects
//
TransitionTime daylightTransitionStart;
if (!TransitionTimeFromTimeZoneInformation(timeZoneInformation, out daylightTransitionStart, readStartDate: true))
{
return(null);
}
TransitionTime daylightTransitionEnd;
if (!TransitionTimeFromTimeZoneInformation(timeZoneInformation, out daylightTransitionEnd, readStartDate: false))
{
return(null);
}
if (daylightTransitionStart.Equals(daylightTransitionEnd))
{
// this happens when the time zone does support DST but the OS has DST disabled
return(null);
}
return(AdjustmentRule.CreateAdjustmentRule(
startDate,
endDate,
new TimeSpan(0, -timeZoneInformation.DaylightBias, 0),
daylightTransitionStart,
daylightTransitionEnd,
new TimeSpan(0, defaultBaseUtcOffset - timeZoneInformation.Bias, 0),
noDaylightTransitions: false));
}
/// <summary>
/// Helper function that takes a string representing a <time_zone_name> registry key name
/// and returns a TimeZoneInfo instance.
/// </summary>
private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo value, out Exception e)
{
e = null;
// Standard Time Zone Registry Data
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
// HKLM
// Software
// Microsoft
// Windows NT
// CurrentVersion
// Time Zones
// <time_zone_name>
// * STD, REG_SZ "Standard Time Name"
// (For OS installed zones, this will always be English)
// * MUI_STD, REG_SZ "@tzres.dll,-1234"
// Indirect string to localized resource for Standard Time,
// add "%windir%\system32\" after "@"
// * DLT, REG_SZ "Daylight Time Name"
// (For OS installed zones, this will always be English)
// * MUI_DLT, REG_SZ "@tzres.dll,-1234"
// Indirect string to localized resource for Daylight Time,
// add "%windir%\system32\" after "@"
// * Display, REG_SZ "Display Name like (GMT-8:00) Pacific Time..."
// * MUI_Display, REG_SZ "@tzres.dll,-1234"
// Indirect string to localized resource for the Display,
// add "%windir%\system32\" after "@"
// * TZI, REG_BINARY REG_TZI_FORMAT
// See Win32Native.RegistryTimeZoneInformation
//
using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id, writable: false))
{
if (key == null)
{
value = null;
return(TimeZoneInfoResult.TimeZoneNotFoundException);
}
Win32Native.RegistryTimeZoneInformation defaultTimeZoneInformation;
byte[] regValue = key.GetValue(TimeZoneInfoValue, null, RegistryValueOptions.None) as byte[];
if (regValue == null || regValue.Length != RegByteLength)
{
// the registry value could not be cast to a byte array
value = null;
return(TimeZoneInfoResult.InvalidTimeZoneException);
}
defaultTimeZoneInformation = new Win32Native.RegistryTimeZoneInformation(regValue);
AdjustmentRule[] adjustmentRules;
if (!TryCreateAdjustmentRules(id, defaultTimeZoneInformation, out adjustmentRules, out e, defaultTimeZoneInformation.Bias))
{
value = null;
return(TimeZoneInfoResult.InvalidTimeZoneException);
}
string displayName;
string standardName;
string daylightName;
if (!TryGetLocalizedNamesByRegistryKey(key, out displayName, out standardName, out daylightName))
{
value = null;
return(TimeZoneInfoResult.InvalidTimeZoneException);
}
try
{
value = new TimeZoneInfo(
id,
new TimeSpan(0, -(defaultTimeZoneInformation.Bias), 0),
displayName,
standardName,
daylightName,
adjustmentRules,
disableDaylightSavingTime: false);
return(TimeZoneInfoResult.Success);
}
catch (ArgumentException ex)
{
// TimeZoneInfo constructor can throw ArgumentException and InvalidTimeZoneException
value = null;
e = ex;
return(TimeZoneInfoResult.InvalidTimeZoneException);
}
catch (InvalidTimeZoneException ex)
{
// TimeZoneInfo constructor can throw ArgumentException and InvalidTimeZoneException
value = null;
e = ex;
return(TimeZoneInfoResult.InvalidTimeZoneException);
}
}
}
/// <summary> /// Helper function that compares the StandardBias and StandardDate portion a /// TimeZoneInformation struct to a time zone registry entry. /// </summary> private static bool TryCompareStandardDate(Win32Native.TimeZoneInformation timeZone, Win32Native.RegistryTimeZoneInformation registryTimeZoneInfo) => timeZone.Bias == registryTimeZoneInfo.Bias && timeZone.StandardBias == registryTimeZoneInfo.StandardBias && timeZone.StandardDate.Year == registryTimeZoneInfo.StandardDate.Year && timeZone.StandardDate.Month == registryTimeZoneInfo.StandardDate.Month && timeZone.StandardDate.DayOfWeek == registryTimeZoneInfo.StandardDate.DayOfWeek && timeZone.StandardDate.Day == registryTimeZoneInfo.StandardDate.Day && timeZone.StandardDate.Hour == registryTimeZoneInfo.StandardDate.Hour && timeZone.StandardDate.Minute == registryTimeZoneInfo.StandardDate.Minute && timeZone.StandardDate.Second == registryTimeZoneInfo.StandardDate.Second && timeZone.StandardDate.Milliseconds == registryTimeZoneInfo.StandardDate.Milliseconds;
/// <summary>
/// Helper function that takes:
/// 1. A string representing a <time_zone_name> registry key name.
/// 2. A RegistryTimeZoneInformation struct containing the default rule.
/// 3. An AdjustmentRule[] out-parameter.
/// </summary>
private static bool TryCreateAdjustmentRules(string id, Win32Native.RegistryTimeZoneInformation defaultTimeZoneInformation, out AdjustmentRule[] rules, out Exception e, int defaultBaseUtcOffset)
{
e = null;
try
{
// Optional, Dynamic Time Zone Registry Data
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
//
// HKLM
// Software
// Microsoft
// Windows NT
// CurrentVersion
// Time Zones
// <time_zone_name>
// Dynamic DST
// * "FirstEntry" REG_DWORD "1980"
// First year in the table. If the current year is less than this value,
// this entry will be used for DST boundaries
// * "LastEntry" REG_DWORD "2038"
// Last year in the table. If the current year is greater than this value,
// this entry will be used for DST boundaries"
// * "<year1>" REG_BINARY REG_TZI_FORMAT
// See Win32Native.RegistryTimeZoneInformation
// * "<year2>" REG_BINARY REG_TZI_FORMAT
// See Win32Native.RegistryTimeZoneInformation
// * "<year3>" REG_BINARY REG_TZI_FORMAT
// See Win32Native.RegistryTimeZoneInformation
//
using (RegistryKey dynamicKey = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive + "\\" + id + "\\Dynamic DST", writable: false))
{
if (dynamicKey == null)
{
AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(
defaultTimeZoneInformation, DateTime.MinValue.Date, DateTime.MaxValue.Date, defaultBaseUtcOffset);
rules = rule == null ? null : new[] { rule };
return(true);
}
//
// loop over all of the "<time_zone_name>\Dynamic DST" hive entries
//
// read FirstEntry {MinValue - (year1, 12, 31)}
// read MiddleEntry {(yearN, 1, 1) - (yearN, 12, 31)}
// read LastEntry {(yearN, 1, 1) - MaxValue }
// read the FirstEntry and LastEntry key values (ex: "1980", "2038")
int first = (int)dynamicKey.GetValue(FirstEntryValue, -1, RegistryValueOptions.None);
int last = (int)dynamicKey.GetValue(LastEntryValue, -1, RegistryValueOptions.None);
if (first == -1 || last == -1 || first > last)
{
rules = null;
return(false);
}
// read the first year entry
Win32Native.RegistryTimeZoneInformation dtzi;
byte[] regValue = dynamicKey.GetValue(first.ToString(CultureInfo.InvariantCulture), null, RegistryValueOptions.None) as byte[];
if (regValue == null || regValue.Length != RegByteLength)
{
rules = null;
return(false);
}
dtzi = new Win32Native.RegistryTimeZoneInformation(regValue);
if (first == last)
{
// there is just 1 dynamic rule for this time zone.
AdjustmentRule rule = CreateAdjustmentRuleFromTimeZoneInformation(dtzi, DateTime.MinValue.Date, DateTime.MaxValue.Date, defaultBaseUtcOffset);
rules = rule == null ? null : new[] { rule };
return(true);
}
List <AdjustmentRule> rulesList = new List <AdjustmentRule>(1);
// there are more than 1 dynamic rules for this time zone.
AdjustmentRule firstRule = CreateAdjustmentRuleFromTimeZoneInformation(
dtzi,
DateTime.MinValue.Date, // MinValue
new DateTime(first, 12, 31), // December 31, <FirstYear>
defaultBaseUtcOffset);
if (firstRule != null)
{
rulesList.Add(firstRule);
}
// read the middle year entries
for (int i = first + 1; i < last; i++)
{
regValue = dynamicKey.GetValue(i.ToString(CultureInfo.InvariantCulture), null, RegistryValueOptions.None) as byte[];
if (regValue == null || regValue.Length != RegByteLength)
{
rules = null;
return(false);
}
dtzi = new Win32Native.RegistryTimeZoneInformation(regValue);
AdjustmentRule middleRule = CreateAdjustmentRuleFromTimeZoneInformation(
dtzi,
new DateTime(i, 1, 1), // January 01, <Year>
new DateTime(i, 12, 31), // December 31, <Year>
defaultBaseUtcOffset);
if (middleRule != null)
{
rulesList.Add(middleRule);
}
}
// read the last year entry
regValue = dynamicKey.GetValue(last.ToString(CultureInfo.InvariantCulture), null, RegistryValueOptions.None) as byte[];
dtzi = new Win32Native.RegistryTimeZoneInformation(regValue);
if (regValue == null || regValue.Length != RegByteLength)
{
rules = null;
return(false);
}
AdjustmentRule lastRule = CreateAdjustmentRuleFromTimeZoneInformation(
dtzi,
new DateTime(last, 1, 1), // January 01, <LastYear>
DateTime.MaxValue.Date, // MaxValue
defaultBaseUtcOffset);
if (lastRule != null)
{
rulesList.Add(lastRule);
}
// convert the ArrayList to an AdjustmentRule array
rules = rulesList.ToArray();
if (rules != null && rules.Length == 0)
{
rules = null;
}
} // end of: using (RegistryKey dynamicKey...
}
catch (InvalidCastException ex)
{
// one of the RegistryKey.GetValue calls could not be cast to an expected value type
rules = null;
e = ex;
return(false);
}
catch (ArgumentOutOfRangeException ex)
{
rules = null;
e = ex;
return(false);
}
catch (ArgumentException ex)
{
rules = null;
e = ex;
return(false);
}
return(true);
}
/// <summary>
/// Converts a Win32Native.RegistryTimeZoneInformation (REG_TZI_FORMAT struct) to a TransitionTime
/// - When the argument 'readStart' is true the corresponding daylightTransitionTimeStart field is read
/// - When the argument 'readStart' is false the corresponding dayightTransitionTimeEnd field is read
/// </summary>
private static bool TransitionTimeFromTimeZoneInformation(Win32Native.RegistryTimeZoneInformation timeZoneInformation, out TransitionTime transitionTime, bool readStartDate)
{
//
// SYSTEMTIME -
//
// If the time zone does not support daylight saving time or if the caller needs
// to disable daylight saving time, the wMonth member in the SYSTEMTIME structure
// must be zero. If this date is specified, the DaylightDate value in the
// TIME_ZONE_INFORMATION structure must also be specified. Otherwise, the system
// assumes the time zone data is invalid and no changes will be applied.
//
bool supportsDst = (timeZoneInformation.StandardDate.Month != 0);
if (!supportsDst)
{
transitionTime = default(TransitionTime);
return(false);
}
//
// SYSTEMTIME -
//
// * FixedDateRule -
// If the Year member is not zero, the transition date is absolute; it will only occur one time
//
// * FloatingDateRule -
// To select the correct day in the month, set the Year member to zero, the Hour and Minute
// members to the transition time, the DayOfWeek member to the appropriate weekday, and the
// Day member to indicate the occurence of the day of the week within the month (first through fifth).
//
// Using this notation, specify the 2:00a.m. on the first Sunday in April as follows:
// Hour = 2,
// Month = 4,
// DayOfWeek = 0,
// Day = 1.
//
// Specify 2:00a.m. on the last Thursday in October as follows:
// Hour = 2,
// Month = 10,
// DayOfWeek = 4,
// Day = 5.
//
if (readStartDate)
{
//
// read the "daylightTransitionStart"
//
if (timeZoneInformation.DaylightDate.Year == 0)
{
transitionTime = TransitionTime.CreateFloatingDateRule(
new DateTime(1, /* year */
1, /* month */
1, /* day */
timeZoneInformation.DaylightDate.Hour,
timeZoneInformation.DaylightDate.Minute,
timeZoneInformation.DaylightDate.Second,
timeZoneInformation.DaylightDate.Milliseconds),
timeZoneInformation.DaylightDate.Month,
timeZoneInformation.DaylightDate.Day, /* Week 1-5 */
(DayOfWeek)timeZoneInformation.DaylightDate.DayOfWeek);
}
else
{
transitionTime = TransitionTime.CreateFixedDateRule(
new DateTime(1, /* year */
1, /* month */
1, /* day */
timeZoneInformation.DaylightDate.Hour,
timeZoneInformation.DaylightDate.Minute,
timeZoneInformation.DaylightDate.Second,
timeZoneInformation.DaylightDate.Milliseconds),
timeZoneInformation.DaylightDate.Month,
timeZoneInformation.DaylightDate.Day);
}
}
else
{
//
// read the "daylightTransitionEnd"
//
if (timeZoneInformation.StandardDate.Year == 0)
{
transitionTime = TransitionTime.CreateFloatingDateRule(
new DateTime(1, /* year */
1, /* month */
1, /* day */
timeZoneInformation.StandardDate.Hour,
timeZoneInformation.StandardDate.Minute,
timeZoneInformation.StandardDate.Second,
timeZoneInformation.StandardDate.Milliseconds),
timeZoneInformation.StandardDate.Month,
timeZoneInformation.StandardDate.Day, /* Week 1-5 */
(DayOfWeek)timeZoneInformation.StandardDate.DayOfWeek);
}
else
{
transitionTime = TransitionTime.CreateFixedDateRule(
new DateTime(1, /* year */
1, /* month */
1, /* day */
timeZoneInformation.StandardDate.Hour,
timeZoneInformation.StandardDate.Minute,
timeZoneInformation.StandardDate.Second,
timeZoneInformation.StandardDate.Milliseconds),
timeZoneInformation.StandardDate.Month,
timeZoneInformation.StandardDate.Day);
}
}
return(true);
}
