儲存和還原時區

發行項
05/22/2023

TimeZoneInfo 類別依賴登錄來擷取預先定義的時區資料。不過，登錄是動態結構。此外，作業系統主要使用此次登錄所包含的時區資訊來處理目前年份的時間調整和轉換。這對依賴精確時區資料的應用程式有兩個主要影響：

應用程式所需的時區可能不會在登錄中定義，或可能已重新命名或從登錄中移除。
登錄中定義的時區可能缺少歷史時區轉換所需的特定調整規則相關資訊。

TimeZoneInfo 類別透過支援序列化 (儲存) 和還原序列化 (還原) 時區資料來解決這些限制。

時區序列化與還原序列化

藉由序列化和還原序列化時區資料來儲存和還原時區，僅涉及兩個方法呼叫：

您可以藉由呼叫物件的 ToSerializedString 方法，序列化 TimeZoneInfo 物件。方法不會採用任何參數，並傳回包含時區資訊的字串。
您可以將該字串傳遞至 static (Visual Basic 中的 Shared) TimeZoneInfo.FromSerializedString 方法，以從序列化字串還原序列化 TimeZoneInfo 物件。

序列化與還原序列化案例

可將 TimeZoneInfo 物件儲存 (序列化) 為字串，或將其還原 (或還原序列化) 以供稍後使用，這會提升 TimeZoneInfo 類別的實用性和彈性。本節會檢查序列化和還原序列化最有用的一些情況。

序列化和還原序列化應用程式中的時區資料

需要時，可以從字串還原序列化的時區。如果從登錄擷取的時區無法正確轉換特定日期範圍內的日期和時間，應用程式可能會這樣做。例如，Windows XP 登錄中的時區資料支援單一調整規則，而 Windows Vista 登錄中定義的時區通常會提供兩個調整規則的相關資訊。這表示歷程記錄時間轉換可能不正確。時區資料的序列化和還原序列化可以處理這項限制。

在下列範例中，所定義的自訂 TimeZoneInfo 類別沒有調整規則，該類別代表從 1883 到 1917 年，日光節約時間推行之前的美國東部標準時間時區。自訂時區會在具有全域範圍的變數中序列化。時區轉換方法 ConvertUtcTime 會傳遞國際標準時間 (UTC) 的時間以進行轉換。如果日期和時間發生在 1917 或更早的版本中，自訂的東部標準時區會從序列化字串還原，並取代從登錄擷取的時區。

using System;

public class TimeZoneSerialization
{
   static string serializedEst;

   public static void Main()
   {
      // Retrieve Eastern Standard Time zone from registry
      try
      {
         TimeZoneSerialization tzs = new TimeZoneSerialization();
         TimeZoneInfo est = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");
         // Create custom Eastern Time Zone for historical (pre-1918) conversions
         CreateTimeZone();
         // Call conversion function with one current and one pre-1918 date and time
         Console.WriteLine(ConvertUtcTime(DateTime.UtcNow, est));
         Console.WriteLine(ConvertUtcTime(new DateTime(1900, 11, 15, 9, 32, 00, DateTimeKind.Utc), est));
      }
      catch (TimeZoneNotFoundException)
      {
         Console.WriteLine("The Eastern Standard Time zone is not in the registry.");
      }
      catch (InvalidTimeZoneException)
      {
         Console.WriteLine("Data on the Eastern Standard Time Zone in the registry is corrupted.");
      }
   }

   private static void CreateTimeZone()
   {
      // Create a simple Eastern Standard time zone
      // without adjustment rules for 1883-1918
      TimeZoneInfo earlyEstZone = TimeZoneInfo.CreateCustomTimeZone("Eastern Standard Time",
                                      new TimeSpan(-5, 0, 0),
                                      " (GMT-05:00) Eastern Time (United States)",
                                      "Eastern Standard Time");
      serializedEst = earlyEstZone.ToSerializedString();
   }

   private static DateTime ConvertUtcTime(DateTime utcDate, TimeZoneInfo tz)
   {
      // Use time zone object from registry
      if (utcDate.Year > 1917)
      {
         return TimeZoneInfo.ConvertTimeFromUtc(utcDate, tz);
      }
      // Handle dates before introduction of DST
      else
      {
         // Restore serialized time zone object
         tz = TimeZoneInfo.FromSerializedString(serializedEst);
         return TimeZoneInfo.ConvertTimeFromUtc(utcDate, tz);
      }
   }
}

Module TimeZoneSerialization
    Dim serializedEst As String

    Public Sub Main()
        ' Retrieve Eastern Standard Time zone from registry
        Try
            Dim est As TimeZoneInfo = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time")
            ' Create custom Eastern Time Zone for historical (pre-1918) conversions
            CreateTimeZone()
            ' Call conversion function with one current and one pre-1918 date and time
            Console.WriteLine(ConvertUtcTime(Date.UtcNow, est))
            Console.WriteLine(ConvertUtcTime(New Date(1900, 11, 15, 9, 32, 00, DateTimeKind.Utc), est))
        Catch e As TimeZoneNotFoundException
            Console.WriteLine("The Eastern Standard Time zone is not in the registry.")
        Catch e As InvalidTimeZoneException
            Console.WriteLine("Data on the Eastern Standard Time Zone in the registry is corrupted.")
        End Try
    End Sub

    Private Sub CreateTimeZone()
        ' Create a simple Eastern Standard time zone 
        ' without adjustment rules for 1883-1918
        Dim earlyEstZone As TimeZoneInfo = TimeZoneInfo.CreateCustomTimeZone("Eastern Standard Time", _
                                        New TimeSpan(-5, 0, 0), _
                                        " (GMT-05:00) Eastern Time (United States)", _
                                        "Eastern Standard Time")
        serializedEst = earlyEstZone.ToSerializedString()
    End Sub

    Private Function ConvertUtcTime(utcDate As Date, tz As TimeZoneInfo) As Date
        ' Use time zone object from registry 
        If Year(utcDate) > 1917 Then
            Return TimeZoneInfo.ConvertTimeFromUtc(utcDate, tz)
            ' Handle dates before introduction of DST
        Else
            ' Restore serialized time zone object
            tz = TimeZoneInfo.FromSerializedString(serializedEst)
            Return TimeZoneInfo.ConvertTimeFromUtc(utcDate, tz)
        End If
    End Function
End Module

處理時區例外狀況

由於登錄是動態結構，因此其內容受限於意外或刻意的修改。這表示應該在登錄中定義時區，而且應用程式成功執行所需的時區可能不存在。若不支援時區序列化和還原序列化，您只能選擇處理結束應用程式所產生的 TimeZoneNotFoundException。不過，藉由使用時區序列化和還原序列化，您可以從序列化字串還原所需的時區來處理非預期的 TimeZoneNotFoundException，而且應用程式會繼續執行。

下列範例會建立並序列化自訂的中央標準時區，然後嘗試從登錄擷取中央標準時區。如果擷取作業擲回 TimeZoneNotFoundException 或 InvalidTimeZoneException，則例外處理常式會還原序列化時區。

using System;
using System.Collections.Generic;

public class TimeZoneApplication
{
   // Define collection of custom time zones
   private Dictionary<string, string> customTimeZones = new Dictionary<string, string>();
   private TimeZoneInfo cst;

   public TimeZoneApplication()
   {
      // Create custom Central Standard Time
      //
      // Declare necessary TimeZoneInfo.AdjustmentRule objects for time zone
      TimeZoneInfo customTimeZone;
      TimeSpan delta = new TimeSpan(1, 0, 0);
      TimeZoneInfo.AdjustmentRule adjustment;
      List<TimeZoneInfo.AdjustmentRule> adjustmentList = new List<TimeZoneInfo.AdjustmentRule>();
      // Declare transition time variables to hold transition time information
      TimeZoneInfo.TransitionTime transitionRuleStart, transitionRuleEnd;

      // Define end rule (for 1976-2006)
      transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0), 10, 5, DayOfWeek.Sunday);
      // Define rule (1976-1986)
      transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0), 04, 05, DayOfWeek.Sunday);
      adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(1976, 1, 1), new DateTime(1986, 12, 31), delta, transitionRuleStart, transitionRuleEnd);
      adjustmentList.Add(adjustment);
      // Define rule (1987-2006)
      transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0), 04, 01, DayOfWeek.Sunday);
      adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(1987, 1, 1), new DateTime(2006, 12, 31), delta, transitionRuleStart, transitionRuleEnd);
      adjustmentList.Add(adjustment);
      // Define rule (2007- )
      transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0), 03, 02, DayOfWeek.Sunday);
      transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 2, 0, 0), 11, 01, DayOfWeek.Sunday);
      adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(2007, 01, 01), DateTime.MaxValue.Date, delta, transitionRuleStart, transitionRuleEnd);
      adjustmentList.Add(adjustment);

      // Create custom U.S. Central Standard Time zone
      customTimeZone = TimeZoneInfo.CreateCustomTimeZone("Central Standard Time",
                      new TimeSpan(-6, 0, 0),
                      "(GMT-06:00) Central Time (US Only)", "Central Standard Time",
                      "Central Daylight Time", adjustmentList.ToArray());
      // Add time zone to collection
      customTimeZones.Add(customTimeZone.Id, customTimeZone.ToSerializedString());

      // Create any other required time zones
   }

   public static void Main()
   {
      TimeZoneApplication tza = new TimeZoneApplication();
      tza.AppEntryPoint();
   }

   private void AppEntryPoint()
   {
      try
      {
         cst = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");
      }
      catch (TimeZoneNotFoundException)
      {
         if (customTimeZones.ContainsKey("Central Standard Time"))
            HandleTimeZoneException("Central Standard Time");
      }
      catch (InvalidTimeZoneException)
      {
         if (customTimeZones.ContainsKey("Central Standard Time"))
            HandleTimeZoneException("Central Standard Time");
      }
      if (cst == null)
      {
         Console.WriteLine("Unable to load Central Standard Time zone.");
         return;
      }
      DateTime currentTime = DateTime.Now;
      Console.WriteLine("The current {0} time is {1}.",
                        TimeZoneInfo.Local.IsDaylightSavingTime(currentTime) ?
                            TimeZoneInfo.Local.StandardName :
                            TimeZoneInfo.Local.DaylightName,
                        currentTime.ToString("f"));
      Console.WriteLine("The current {0} time is {1}.",
                        cst.IsDaylightSavingTime(currentTime) ?
                            cst.StandardName :
                            cst.DaylightName,
                        TimeZoneInfo.ConvertTime(currentTime, TimeZoneInfo.Local, cst).ToString("f"));
   }

   private void HandleTimeZoneException(string timeZoneName)
   {
      string tzString = customTimeZones[timeZoneName];
      cst = TimeZoneInfo.FromSerializedString(tzString);
   }
}

Imports System.Collections.Generic

Public Class TimeZoneApplication
    ' Define collection of custom time zones
    Private customTimeZones As New Dictionary(Of String, String)
    Private cst As TimeZoneInfo

    Public Sub New()
        ' Define custom Central Standard Time
        '
        ' Declare necessary TimeZoneInfo.AdjustmentRule objects for time zone
        Dim customTimeZone As TimeZoneInfo
        Dim delta As New TimeSpan(1, 0, 0)
        Dim adjustment As TimeZoneInfo.AdjustmentRule
        Dim adjustmentList As New List(Of TimeZoneInfo.AdjustmentRule)
        ' Declare transition time variables to hold transition time information
        Dim transitionRuleStart, transitionRuleEnd As TimeZoneInfo.TransitionTime

        ' Define end rule (for 1976-2006)
        transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(#02:00:00AM#, 10, 5, DayOfWeek.Sunday)
        ' Define rule (1976-1986)
        transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(#2:00:00AM#, 04, 05, DayOfWeek.Sunday)
        adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(#01/01/1976#, #12/31/1986#, delta, transitionRuleStart, transitionRuleEnd)
        adjustmentList.Add(adjustment)
        ' Define rule (1987-2006)  
        transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(#2:00:00AM#, 04, 01, DayOfWeek.Sunday)
        adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(#01/01/1987#, #12/31/2006#, delta, transitionRuleStart, transitionRuleEnd)
        adjustmentList.Add(adjustment)
        ' Define rule (2007- )  
        transitionRuleStart = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(#2:00:00AM#, 03, 02, DayOfWeek.Sunday)
        transitionRuleEnd = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(#2:00:00AM#, 11, 01, DayOfWeek.Sunday)
        adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(#01/01/2007#, Date.MaxValue.Date, delta, transitionRuleStart, transitionRuleEnd)
        adjustmentList.Add(adjustment)
        ' Create custom time zone
        customTimeZone = TimeZoneInfo.CreateCustomTimeZone("Central Standard Time", _
                        New TimeSpan(-6, 0, 0), _
                        "(GMT-06:00) Central Time (US Only)", "Central Standard Time", _
                        "Central Daylight Time", adjustmentList.ToArray())
        ' Add time zone to collection
        customTimeZones.Add(customTimeZone.Id, customTimeZone.ToSerializedString())

        ' Create any other required time zones     
    End Sub

    Public Shared Sub Main()
        Dim tza As New TimeZoneApplication()
        tza.AppEntryPoint()
    End Sub

    Private Sub AppEntryPoint()
        Try
            cst = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time")
        Catch e As TimeZoneNotFoundException
            If customTimeZones.ContainsKey("Central Standard Time")
                HandleTimeZoneException("Central Standard Time")
            End If
        Catch e As InvalidTimeZoneException
            If customTimeZones.ContainsKey("Central Standard Time")
                HandleTimeZoneException("Central Standard Time")
            End If
        End Try
        If cst Is Nothing Then
            Console.WriteLine("Unable to load Central Standard Time zone.")
            Return
        End If
        Dim currentTime As Date = Date.Now
        Console.WriteLine("The current {0} time is {1}.", _
                          IIf(TimeZoneInfo.Local.IsDaylightSavingTime(currentTime), _
                              TimeZoneInfo.Local.StandardName, _
                              TimeZoneInfo.Local.DaylightName), _
                          currentTime.ToString("f"))
        Console.WriteLine("The current {0} time is {1}.", _
                          IIf(cst.IsDaylightSavingTime(currentTime), _
                              cst.StandardName, _
                              cst.DaylightName), _
                          TimeZoneInfo.ConvertTime(currentTime, TimeZoneInfo.Local, cst).ToString("f"))
    End Sub

    Private Sub HandleTimeZoneException(timeZoneName As String)
        Dim tzString As String = customTimeZones.Item(timeZoneName)
        cst = TimeZoneInfo.FromSerializedString(tzString)
    End Sub
End Class

儲存序列化字串，並視需要還原該字串

上述範例已將時區資訊儲存至字串變數，並在需要時加以還原。不過，包含序列化時區資訊的字串本身可以儲存在某些儲存媒體中，例如外部檔案、應用程式內嵌的資源檔案或登錄。 (請注意，自訂時區的相關資訊應該與登錄中的系統時區索引鍵分開儲存。)

以這種方式儲存序列化的時區字串，也會分隔時區建立常式與應用程式本身。例如，時區建立常式可以執行並建立資料檔案，其中包含應用程式可使用的歷史時區資訊。接著，資料檔案可隨應用程式一併安裝且可開啟，當應用程式需要其時區時，可將一或多個時區還原序列化。

如需使用內嵌資源來儲存序列化時區資料的範例，請參閱操作說明：將時區儲存到內嵌資源，以及操作說明：從內嵌資源還原時區。

另請參閱

日期、時間及時區

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