我们有一个系统,用UTC时间表示从美国/芝加哥时区开始和结束日期时间的周。周从中央时间星期六凌晨零点开始,到中央时间星期五晚上23:59:59结束,因此它们在数据库中的UTC条目为:
Week 1 - begin: 2015-10-24 05:00:00, end 2015-10-31 04:59:59
Week 2 - begin: 2015-10-31 05:00:00, end 2015-11-07 05:59:59
Week 3 - begin: 2015-11-07 06:00:00, end 2015-11-14 05:59:59
Week 4 - begin: 2015-11-14 06:00:00, end 2015-11-21 05:59:59
Week 5 - begin: 2015-11-21 06:00:00, end 2015-11-28 05:59:59
从上面的例子可以看到,夏令时和标准时间之间的时间变化在10月31日至11月7日期间反映出来。
我需要返回一个给定周之前的N周。我们的系统是C# Azure工作和Web角色,并在Azure云中运行(所有计算节点都是UTC)。我的逻辑是,取开始周,添加N周的工作日到该周的开始日期/时间,并请求开始日期大于原始开始日期且小于或等于计算得出的未来日期的周。
var weeks = repository.Fetch(x => x.BeginDate <= nWeeksAheadUtc && x.BeginDate > week.BeginDate)l=;
这个方法是行得通的,除了当夏令时改变但答案没有反应出来的时候。由于时间变化,只基于向第1周的开始日期添加21天并要求接下来的3周结果只返回第2和第3周,因为计算未来值是2015-11-14 05:00:00,它不包括第4周。
我已经使用Nodatime以以下方式解决了这个问题:
LocalDateTime localDateTime = LocalDateTime.FromDateTime(week.BeginDate);
ZonedDateTime zonedDateTime = localDateTime.InZoneStrictly(DateTimeZoneProviders.Tzdb["UTC"]);
zonedDateTime = zonedDateTime.WithZone(DateTimeZoneProviders.Tzdb["America/Chicago"]);
DateTime centralDateTime = zonedDateTime.ToDateTimeUnspecified();
DateTime futureDateTime = centralDateTime.Add(TimeSpan.FromDays(weekCount*7));
localDateTime = LocalDateTime.FromDateTime(futureDateTime);
zonedDateTime = localDateTime.InZoneStrictly(DateTimeZoneProviders.Tzdb["America/Chicago"]);
DateTime nWeeksAheadUtc = zonedDateTime.ToDateTimeUtc();
var weeks = repository.Fetch(x => x.BeginDate <= nWeeksAheadUtc && x.BeginDate > week.BeginDate).OrderBy(x => x.RetailerWeekNumber).ToList();
虽然它可以正常运行,但对于跟随我维护此代码的开发人员来说,似乎笨重且不太直观。是否有更清晰的方法通过Nodatime API或(基本的C#日期/时间)来完成这个任务,我是否遗漏了什么?
添加所请求的示例 - 我刚为此创建了一个Unit测试项目,并编写了以下三个类:
Week.cs
using System;
namespace NodaTimeTest
{
public class Week
{
public int Id { get; set; }
public DateTime BeginDate { get; set; }
public DateTime EndDate { get; set; }
}
}
WeekService.cs
using NodaTime;
using System;
using System.Collections.Generic;
using System.Linq;
namespace NodaTimeTest
{
public class WeekService
{
private readonly List<Week> repository;
public WeekService()
{
this.repository = this.InitWeeks();
}
public List<Week> GetNextWeeks(int weekId, int weekCount)
{
Week week = this.repository.First(x => x.Id == weekId);
// the meat - how to do this the right way?
LocalDateTime localDateTime = LocalDateTime.FromDateTime(week.BeginDate);
ZonedDateTime zonedDateTime = localDateTime.InZoneStrictly(DateTimeZoneProviders.Tzdb["UTC"]);
zonedDateTime = zonedDateTime.WithZone(DateTimeZoneProviders.Tzdb["America/Chicago"]);
DateTime centralDateTime = zonedDateTime.ToDateTimeUnspecified();
DateTime futureDateTime = centralDateTime.Add(TimeSpan.FromDays(weekCount * 7));
localDateTime = LocalDateTime.FromDateTime(futureDateTime);
zonedDateTime = localDateTime.InZoneStrictly(DateTimeZoneProviders.Tzdb["America/Chicago"]);
DateTime nWeeksAheadUtc = zonedDateTime.ToDateTimeUtc();
var weeks = repository.Where(x => x.BeginDate <= nWeeksAheadUtc && x.BeginDate > week.BeginDate).OrderBy(x => x.Id).ToList();
return weeks;
}
private List<Week> InitWeeks()
{
// sets up our list of 10 example dates in UTC encompassing America/Chicago daylight savings time change on 11/1
// this means that all weeks are 168 hours long, except week "4", which is 169 hours long.
var weeks = new List<Week>();
DateTime beginDate = new DateTime(2015, 10, 10, 5, 0, 0, DateTimeKind.Utc);
for (int i = 1; i <= 10; i++)
{
DateTime endDate = beginDate.AddDays(7).AddSeconds(-1);
if (endDate.Date == new DateTime(2015, 11, 7, 0, 0, 0, DateTimeKind.Utc))
{
endDate = endDate.AddHours(1);
}
weeks.Add(new Week { Id = i, BeginDate = beginDate, EndDate = endDate });
beginDate = endDate.AddSeconds(1);
}
return weeks;
}
}
}
WeekServiceTest:
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Linq;
namespace NodaTimeTest
{
[TestClass]
public class WeekServiceTest
{
private readonly WeekService weekService = new WeekService();
[TestMethod]
public void TestGetNextThreeWeeksOverDaylightTimeChange()
{
var result = this.weekService.GetNextWeeks(2, 3);
Assert.AreEqual(3, result.ElementAt(0).Id);
Assert.AreEqual(4, result.ElementAt(1).Id);
Assert.AreEqual(5, result.ElementAt(2).Id);
}
[TestMethod]
public void TestGetNextThreeWeeksWithNoDaylightTimeChange()
{
var result = this.weekService.GetNextWeeks(5, 3);
Assert.AreEqual(6, result.ElementAt(0).Id);
Assert.AreEqual(7, result.ElementAt(1).Id);
Assert.AreEqual(8, result.ElementAt(2).Id);
}
}
}