C# 2.0 特定时区

Question

我正在 .NET 2.0 中开发一个遗留应用程序，我想将时间从本地时间（恰好是 UTC+1）转换为巴西时间（即 Windows 所说的“南美洲东部标准时间”）然后回来。

我将我想出的代码放在一起进行转换：

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using Microsoft.Win32;

namespace timezone
{
 class Program
 {
  [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = false)]
  private static extern int SystemTimeToTzSpecificLocalTime(ref
   TIME_ZONE_INFORMATION lpTimeZone, ref SYSTEMTIME lpUniversalTIme, out
   SYSTEMTIME lpLocalTime);

  [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = false)]
  private static extern int TzSpecificLocalTimeToSystemTime(ref
   TIME_ZONE_INFORMATION lpTimeZone, ref SYSTEMTIME lpLocalTime, out SYSTEMTIME
   lpUniversalTIme);

  [DllImport("kernel32.dll")]
  private static extern void GetSystemTime(out SYSTEMTIME lpSystemTime);

  [StructLayout(LayoutKind.Sequential)]
  private struct SYSTEMTIME
  {
   public ushort wYear;
   public ushort wMonth;
   public ushort wDayOfWeek;
   public ushort wDay;
   public ushort wHour;
   public ushort wMinute;
   public ushort wSecond;
   public ushort wMilliseconds;
  }

  //Registry time zone format. See KB article Q115231
  [StructLayout(LayoutKind.Sequential)]
  private struct REG_TIME_ZONE_INFORMATION
  {
   public int Bias;
   public int StandardBias;
   public int DaylightBias;
   public SYSTEMTIME StandardDate;
   public SYSTEMTIME DaylightDate;
  }

  [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
  private struct TIME_ZONE_INFORMATION
  {
   public int Bias;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
   public string StandardName;
   public SYSTEMTIME StandardDate;
   public int StandardBias;
   [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
   public string DaylightName;
   public SYSTEMTIME DaylightDate;
   public int DaylightBias;
  }

  private static List<TIME_ZONE_INFORMATION> GetTimeZones()
  {
   List<TIME_ZONE_INFORMATION> list = new List<TIME_ZONE_INFORMATION>();
   RegistryKey key =
   Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones");
   if (key == null)
    return list;

   string[] subKeyNames = key.GetSubKeyNames();
   foreach (string subKeyName in subKeyNames)
   {
    RegistryKey subKey = key.OpenSubKey(subKeyName);
    if (subKey != null)
    {
     object value = subKey.GetValue("TZI");
     if (value != null)
     {
      int length =
      Marshal.SizeOf(typeof(REG_TIME_ZONE_INFORMATION));
      IntPtr p = Marshal.AllocHGlobal(length);
      Marshal.Copy((byte[])value, 0, p, length);
      REG_TIME_ZONE_INFORMATION rtzi =
      (REG_TIME_ZONE_INFORMATION)Marshal.PtrToStructure(p,
      typeof(REG_TIME_ZONE_INFORMATION));
      Marshal.FreeHGlobal(p);

      TIME_ZONE_INFORMATION tzi = new TIME_ZONE_INFORMATION();
      tzi.Bias = rtzi.Bias;
      tzi.DaylightBias = rtzi.DaylightBias;
      tzi.StandardBias = rtzi.StandardBias;
      tzi.DaylightDate = rtzi.DaylightDate;
      tzi.StandardDate = rtzi.StandardDate;
      tzi.DaylightName = (string)subKey.GetValue("Dlt", "");
      tzi.StandardName = (string)subKey.GetValue("Std", "");
      list.Add(tzi);
     }
     subKey.Close();
    }
   }
   key.Close();
   return list;
  }

  static void Main(string[] args)
  {
   foreach (TIME_ZONE_INFORMATION tzi in GetTimeZones())
   {
    if ("E. South America Standard Time" == tzi.StandardName)
    {
     Console.WriteLine("local time: " + DateTime.Now);
     Console.WriteLine("name: {0} st bias:{1} daylight date:{2}-{3}-{4}, bias:{5}", tzi.StandardName, tzi.DaylightBias, tzi.DaylightDate.wDay, tzi.DaylightDate.wMonth, tzi.DaylightDate.wYear, tzi.Bias);
     TIME_ZONE_INFORMATION tzi2 = tzi; //local copy so that i can pass it as a ref
     SYSTEMTIME braziltime = new SYSTEMTIME();
     SYSTEMTIME localtime = new SYSTEMTIME();
     GetSystemTime(out localtime);
     SystemTimeToTzSpecificLocalTime(ref tzi2, ref localtime, out braziltime);
     Console.WriteLine("{0}:{1}", braziltime.wHour, braziltime.wMinute);
     Console.WriteLine("{0}-{1}-{2} {3}:{4}:{5}", braziltime.wYear, braziltime.wMonth, braziltime.wDay, braziltime.wHour, braziltime.wMinute, braziltime.wSecond);
     DateTime dt = DateTime.Now;
     braziltime.wYear = (ushort)dt.Year;
     braziltime.wMonth = (ushort)dt.Month;
     braziltime.wDay = (ushort)dt.Day;
     braziltime.wHour = (ushort)(dt.Hour - 3); //today the timezone difference is 3 hours
     braziltime.wMinute = (ushort)dt.Minute;
     braziltime.wSecond = (ushort)dt.Second;
     TzSpecificLocalTimeToSystemTime(ref tzi2, ref braziltime, out localtime);
     Console.WriteLine("{0}-{1}-{2} {3}:{4}:{5}", localtime.wYear, localtime.wMonth, localtime.wDay, localtime.wHour, localtime.wMinute, localtime.wSecond);
     break;
    }
   }
   Console.ReadLine();
  }
 }
}

但是我得到了这个输出：

local time: 11/22/2010 11:55:15 AM
name: E. South America Standard Time st bias:-60 daylight date:3-10-0, bias:180 8:55
2010-11-22 8:55:15
2010-11-22 10:55:15

所以我将当地时间转换为巴西时间并返回，并减少一个小时。 任何想法有什么问题吗？

Answer 1

我认为您期望输出的第一行与最后一行匹配。这种情况没有发生，因为第一行写的是当地时间。然后，您调用 GetSystemTime 并将该值转换为巴西时间，然后再转换回来。 GetSystemTime 返回 UTC，因此您返回并在最后一行输出的值也应该是 UTC。换句话说，你不是在比较同类。

如果您在调用 GetSystemTime 之后立即输出本地时间的值，您应该会看到该值与转换后的输出值匹配。

如果您想从本地时间转换为巴西时间，那么您可能需要将本地时间转换为 UTC，然后使用每个步骤的相应时区信息将 UTC 转换为巴西时间。

Answer 2

请记住，DateTime 只是一个用于存储日期时间的结构。

您应该在应用程序中的所有位置使用 UTC，并且仅使用 Locale 进行输出。为了干净，我更喜欢大部分时间使用 utc 并从中进行转换。

Answer 3

如果是3.5的话...

using System;

// ReSharper disable once CheckNamespace
public static class BrazilTime
{
    public static DateTime Now
    {
        get
        {
            return TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, TimeZoneInfo.FindSystemTimeZoneById("E. South America Standard Time"));
        }
    }
}