/// <summary>
/// Returns the IDs of all system time zones.
/// </summary>
/// <returns>The IDs available from this source.</returns>
public IEnumerable <string> GetIds()
{
// Always include the local time zone, since Mono may not include it in the list of system time zones, even
// though it allows the Id to be passed to FindSystemTimeZoneById().
// See https://github.com/nodatime/nodatime/issues/235.
return(TimeZoneInfoInterceptor.GetSystemTimeZones()
.Select(zone => zone.Id)
.Union(GetTimeZoneInfoLocalIdOrEmpty()));
}
/// <summary>
/// Creates a new instance of <see cref="BclDateTimeZone" /> from the <see cref="TimeZoneInfo"/> with the given
/// ID. The ID must be a known system time zone ID.
/// </summary>
/// <param name="id">The ID of the system time zone to convert</param>
/// <exception cref="ArgumentException">The given zone doesn't exist.</exception>
/// <returns>The Noda Time representation of the given BCL time zone</returns>
public BclDateTimeZone ForId(string id)
{
try
{
TimeZoneInfo zone = TimeZoneInfoInterceptor.FindSystemTimeZoneById(id);
return(BclDateTimeZone.FromTimeZoneInfo(zone));
}
catch (TimeZoneNotFoundException)
{
throw new ArgumentException(id + " is not a system time zone ID", nameof(id));
}
}
/// <summary>
/// Returns an enumerable containing a singleton element of the Id of the local time zone
/// (<c>TimeZoneInfo.Local.Id</c>), unless the local time zone is not available, or not a system time zone, in
/// which case returns an empty enumerable.
/// </summary>
private static IEnumerable <string> GetTimeZoneInfoLocalIdOrEmpty()
{
// This complexity is entirely to handle Mono, which fails quite badly at this in some cases.
try
{
// May throw TimeZoneNotFoundException, particularly on Mono/Windows.
// See https://bugzilla.xamarin.com/show_bug.cgi?id=11817
var local = TimeZoneInfoInterceptor.Local;
if (local != null) // https://github.com/nodatime/nodatime/issues/235#issuecomment-80932079
{
// Make sure we can look it up again, as there are legitimate cases where the local time zone is not
// a system time zone. If not, this also throws TimeZoneNotFoundException.
TimeZoneInfoInterceptor.FindSystemTimeZoneById(local.Id);
return(new[] { local.Id });
}
}
catch (TimeZoneNotFoundException)
{
}
return(Enumerable.Empty <string>());
}
