使用 DateTime.ParseExact() 的时间解析问题

Question

我将时间值存储为字符串，格式为 HH:mm

我使用以下代码将其解析为日期为 Today Date

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

结果是2017-03-15 09:00:00

当运行此代码来自另一台机器时，我得到以下结果：1899-12-31 09:00:00

我将我的代码替换为以下内容

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

它工作正常，但我仍然想知道为什么每个系统都将日期解析为不同的值？？？

Answer 1

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

下面table描述了获取默认值的行为当缺少某些 year/month/day 值时。
"X" 表示该值存在。而“--”表示缺少值。

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.

使用 DateTime.ParseExact() 的时间解析问题

Time parsing Issue using DateTime.ParseExact()

vb.net

datetime

ssis

etl

script-task