使用DateTime.ParseExact()的时间解析问题 [英] Time parsing Issue using DateTime.ParseExact()

问题描述

我将时间值存储为字符串，格式为HH:mm

I have a Time Value stored as string with the format HH:mm

我使用以下代码将其与今日日期"解析为日期

I used the following code to parse it as date with Today Date

DateTime.ParseExact("09:00","HH:mm",New System.Globalization.CultureInfi("En-GB"))

结果为2017-03-15 09:00:00

从另一台计算机运行此代码时，我得到以下结果:1899-12-31 09:00:00

When Running this Code From another machine i get the following Result: 1899-12-31 09:00:00

我将代码替换为以下内容

I replaced my code to the following

DateTime.ParseExact(DateTime.Now.ToString("yyyy-MM-dd") & " 09:00","yyyy-MM-dd HH:mm",New System.Globalization.CultureInfi("En-GB"))

它可以正常工作，但是我仍然想知道为什么每个系统都将日期解析为不同的值?

推荐答案

DateTime.ParseExact
中缺少的Year/Month/Day的默认值 从.NET源代码:

Default values for missing Year/Month/Day in DateTime.ParseExact
From .NET source code:

下表描述了获取默认值的行为 当缺少某些年/月/日值时.
"X"表示该值存在. -"表示缺少值.

The following table describes the behaviors of getting the default value when a certain year/month/day values are missing.
An "X" means that the value exists. And "--" means that value is missing.

Year    Month   Day =>  ResultYear  ResultMonth     ResultDay       Note

X       X       X       Parsed year Parsed month    Parsed day
X       X       --      Parsed Year Parsed month    First day       If we have year and month, assume the first day of that month.
X       --      X       Parsed year First month     Parsed day      If the month is missing, assume first month of that year.
X       --      --      Parsed year First month     First day       If we have only the year, assume the first day of that year.

--      X       X       CurrentYear Parsed month    Parsed day      If the year is missing, assume the current year.
--      X       --      CurrentYear Parsed month    First day       If we have only a month value, assume the current year and current day.
--      --      X       CurrentYear First month     Parsed day      If we have only a day value, assume current year and first month.
--      --      --      CurrentYear Current month   Current day     So this means that if the date string only contains time, you will get current date.

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