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> /// Helper function to check if the current TimeZoneInformation struct does not support DST. /// This check returns true when the DaylightDate == StandardDate. /// This check is only meant to be used for "Local". /// </summary> private static bool CheckDaylightSavingTimeNotSupported(Win32Native.TimeZoneInformation timeZone) => timeZone.DaylightDate.Year == timeZone.StandardDate.Year && timeZone.DaylightDate.Month == timeZone.StandardDate.Month && timeZone.DaylightDate.DayOfWeek == timeZone.StandardDate.DayOfWeek && timeZone.DaylightDate.Day == timeZone.StandardDate.Day && timeZone.DaylightDate.Hour == timeZone.StandardDate.Hour && timeZone.DaylightDate.Minute == timeZone.StandardDate.Minute && timeZone.DaylightDate.Second == timeZone.StandardDate.Second && timeZone.DaylightDate.Milliseconds == timeZone.StandardDate.Milliseconds;
/// <summary>
/// Helper function for retrieving the local system time zone.
/// May throw COMException, TimeZoneNotFoundException, InvalidTimeZoneException.
/// Assumes cachedData lock is taken.
/// </summary>
/// <returns>A new TimeZoneInfo instance.</returns>
private static TimeZoneInfo GetLocalTimeZone(CachedData cachedData)
{
Debug.Assert(Monitor.IsEntered(cachedData));
string id = null;
//
// Try using the "kernel32!GetDynamicTimeZoneInformation" API to get the "id"
//
var dynamicTimeZoneInformation = new Win32Native.DynamicTimeZoneInformation();
// call kernel32!GetDynamicTimeZoneInformation...
long result = UnsafeNativeMethods.GetDynamicTimeZoneInformation(out dynamicTimeZoneInformation);
if (result == Win32Native.TIME_ZONE_ID_INVALID)
{
// return a dummy entry
return(CreateCustomTimeZone(LocalId, TimeSpan.Zero, LocalId, LocalId));
}
var timeZoneInformation = new Win32Native.TimeZoneInformation(dynamicTimeZoneInformation);
bool dstDisabled = dynamicTimeZoneInformation.DynamicDaylightTimeDisabled;
// check to see if we can use the key name returned from the API call
if (!string.IsNullOrEmpty(dynamicTimeZoneInformation.TimeZoneKeyName))
{
TimeZoneInfo zone;
Exception ex;
if (TryGetTimeZone(dynamicTimeZoneInformation.TimeZoneKeyName, dstDisabled, out zone, out ex, cachedData) == TimeZoneInfoResult.Success)
{
// successfully loaded the time zone from the registry
return(zone);
}
}
// the key name was not returned or it pointed to a bogus entry - search for the entry ourselves
id = FindIdFromTimeZoneInformation(timeZoneInformation, out dstDisabled);
if (id != null)
{
TimeZoneInfo zone;
Exception ex;
if (TryGetTimeZone(id, dstDisabled, out zone, out ex, cachedData) == TimeZoneInfoResult.Success)
{
// successfully loaded the time zone from the registry
return(zone);
}
}
// We could not find the data in the registry. Fall back to using
// the data from the Win32 API
return(GetLocalTimeZoneFromWin32Data(timeZoneInformation, dstDisabled));
}
/// <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 searches the registry for a time zone entry
/// that matches the TimeZoneInformation struct.
/// </summary>
private static string FindIdFromTimeZoneInformation(Win32Native.TimeZoneInformation timeZone, out bool dstDisabled)
{
dstDisabled = false;
using (RegistryKey key = Registry.LocalMachine.OpenSubKey(TimeZonesRegistryHive, writable: false))
{
if (key == null)
{
return(null);
}
foreach (string keyName in key.GetSubKeyNames())
{
if (TryCompareTimeZoneInformationToRegistry(timeZone, keyName, out dstDisabled))
{
return(keyName);
}
}
}
return(null);
}
/// <summary>
/// Helper function used by 'GetLocalTimeZone()' - this function wraps a bunch of
/// try/catch logic for handling the TimeZoneInfo private constructor that takes
/// a Win32Native.TimeZoneInformation structure.
/// </summary>
private static TimeZoneInfo GetLocalTimeZoneFromWin32Data(Win32Native.TimeZoneInformation timeZoneInformation, bool dstDisabled)
{
// first try to create the TimeZoneInfo with the original 'dstDisabled' flag
try
{
return(new TimeZoneInfo(timeZoneInformation, dstDisabled));
}
catch (ArgumentException) { }
catch (InvalidTimeZoneException) { }
// if 'dstDisabled' was false then try passing in 'true' as a last ditch effort
if (!dstDisabled)
{
try
{
return(new TimeZoneInfo(timeZoneInformation, dstDisabled: true));
}
catch (ArgumentException) { }
catch (InvalidTimeZoneException) { }
}
// the data returned from Windows is completely bogus; return a dummy entry
return(CreateCustomTimeZone(LocalId, TimeSpan.Zero, LocalId, LocalId));
}