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How to: Save Time Zones to an Embedded Resource

A time zone-aware application often requires the presence of a particular time zone. However, because the availability of individual TimeZoneInfo objects depends on information stored in the local system's registry, even customarily available time zones may be absent. In addition, information about custom time zones instantiated by using the CreateCustomTimeZone method is not stored with other time zone information in the registry. To ensure that these time zones are available when they are needed, you can save them by serializing them, and later restore them by deserializing them.

Typically, serializing a TimeZoneInfo object occurs apart from the time zone-aware application. Depending on the data store used to hold serialized TimeZoneInfo objects, time zone data may be serialized as part of a setup or installation routine (for example, when the data is stored in an application key of the registry), or as part of a utility routine that runs before the final application is compiled (for example, when the serialized data is stored in a .NET XML resource (.resx) file).

In addition to a resource file that is compiled with the application, several other data stores can be used for time zone information. These include the following:

  • The registry. Note that an application should use the subkeys of its own application key to store custom time zone data rather than using the subkeys of HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones.

  • Configuration files.

  • Other system files.

To save a time zone by serializing it to a .resx file

  1. Retrieve an existing time zone or create a new time zone.

    To retrieve an existing time zone, see How to: Access the Predefined UTC and Local Time Zone Objects and How to: Instantiate a TimeZoneInfo Object.

    To create a new time zone, call one of the overloads of the CreateCustomTimeZone method. For more information, see How to: Create Time Zones Without Adjustment Rules and How to: Create Time Zones with Adjustment Rules.

  2. Call the ToSerializedString method to create a string that contains the time zone's data.

  3. Instantiate a StreamWriter object by providing the name and optionally the path of the .resx file to the StreamWriter class constructor.

  4. Instantiate a ResXResourceWriter object by passing the StreamWriter object to the ResXResourceWriter class constructor.

  5. Pass the time zone's serialized string to the ResXResourceWriter.AddResource method.

  6. Call the ResXResourceWriter.Generate method.

  7. Call the ResXResourceWriter.Close method.

  8. Close the StreamWriter object by calling its Close method.

  9. Add the generated .resx file to the application's Visual Studio project.

  10. Using the Properties window in Visual Studio, make sure that the .resx file's Build Action property is set to Embedded Resource.

The following example serializes a TimeZoneInfo object that represents Central Standard Time and a TimeZoneInfo object that represents the Palmer Station, Antarctica time to a .NET XML resource file that is named SerializedTimeZones.resx. Central Standard Time is typically defined in the registry; Palmer Station, Antarctica is a custom time zone.

TimeZoneSerialization()
{
   TextWriter writeStream;
   Dictionary<string, string> resources = new Dictionary<string, string>();
   // Determine if .resx file exists 
   if (File.Exists(resxName))
   {
      // Open reader
      TextReader readStream = new StreamReader(resxName);
      ResXResourceReader resReader = new ResXResourceReader(readStream);
      foreach (DictionaryEntry item in resReader)
      {
         if (! (((string) item.Key) == "CentralStandardTime" || 
                ((string) item.Key) == "PalmerStandardTime" )) 
            resources.Add((string)item.Key, (string) item.Value);
      }
      readStream.Close();
      // Delete file, since write method creates duplicate xml headers
      File.Delete(resxName);
   }

   // Open stream to write to .resx file 
   try
   {
      writeStream = new StreamWriter(resxName, true);
   }
   catch (FileNotFoundException e)
   {
      // Handle failure to find file
      Console.WriteLine("{0}: The file {1} could not be found.", e.GetType().Name, resxName);
      return;
   }

   // Get resource writer
   ResXResourceWriter resWriter = new ResXResourceWriter(writeStream);

   // Add resources from existing file 
   foreach (KeyValuePair<string, string> item in resources)
   {
      resWriter.AddResource(item.Key, item.Value);
   }

   // Serialize Central Standard Time 
   try
   {
      TimeZoneInfo cst = TimeZoneInfo.FindSystemTimeZoneById("Central Standard Time");
      resWriter.AddResource(cst.Id.Replace(" ", string.Empty), cst.ToSerializedString());
   }
   catch (TimeZoneNotFoundException)
   {
      Console.WriteLine("The Central Standard Time zone could not be found.");
   }

   // Create time zone for Palmer, Antarctica 
   // 
   // Define transition times to/from DST
   TimeZoneInfo.TransitionTime startTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 4, 0, 0), 
                                                                                              10, 2, DayOfWeek.Sunday);
   TimeZoneInfo.TransitionTime endTransition = TimeZoneInfo.TransitionTime.CreateFloatingDateRule(new DateTime(1, 1, 1, 3, 0, 0), 
                                                                                            3, 2, DayOfWeek.Sunday);
   // Define adjustment rule
   TimeSpan delta = new TimeSpan(1, 0, 0);
   TimeZoneInfo.AdjustmentRule adjustment = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(new DateTime(1999, 10, 1), 
                                         DateTime.MaxValue.Date, delta, startTransition, endTransition);
   // Create array for adjustment rules
   TimeZoneInfo.AdjustmentRule[] adjustments = {adjustment};
   // Define other custom time zone arguments 
   string DisplayName = "(GMT-04:00) Antarctica/Palmer Time";
   string standardName = "Palmer Standard Time";
   string daylightName = "Palmer Daylight Time";
   TimeSpan offset = new TimeSpan(-4, 0, 0);
   TimeZoneInfo palmer = TimeZoneInfo.CreateCustomTimeZone(standardName, offset, DisplayName, standardName, daylightName, adjustments);
   resWriter.AddResource(palmer.Id.Replace(" ", String.Empty), palmer.ToSerializedString());

   // Save changes to .resx file 
   resWriter.Generate();
   resWriter.Close();
   writeStream.Close();
}

This example serializes TimeZoneInfo objects so that they are available in a resource file at compile time.

Because the ResXResourceWriter.Generate method adds complete header information to a .NET XML resource file, it cannot be used to add resources to an existing file. The example handles this by checking for the SerializedTimeZones.resx file and, if it exists, storing all of its resources other than the two serialized time zones to a generic Dictionary<TKey, TValue> object. The existing file is then deleted and the existing resources are added to a new SerializedTimeZones.resx file. The serialized time zone data is also added to this file.

The key (or Name) fields of resources should not contain embedded spaces. The Replace(String, String) method is called to remove all embedded spaces in the time zone identifiers before they are assigned to the resource file.

This example requires:

  • That a reference to System.Windows.Forms.dll and System.Core.dll be added to the project.

  • That the following namespaces be imported:

    using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Globalization;
    using System.IO;
    using System.Reflection;
    using System.Resources;
    using System.Windows.Forms;
    
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