Question

VB2012：我正在从遗留系统中读取数据。其中一个字段是时间，我正在将其读入DateTime变量。我使用“hhmmt”格式用DateTime.ParseExact解析日期。我唯一的问题是遗留系统显示A代表AM，P代表PM代表中午N的特殊情况。那么.NET不喜欢N指示符，所以我检测到它并将其改为P.很棒。

003 0300 AAABBB  845A 1200N
005 1400 CCCDDD 1055A  240P
007 7000 EEEFFF  306P  531P

现在我做一些处理并将数据打印到文件中。我想以遗留系统中打印的格式打印出时间。我的第一个想法是使用自定义DateTimeFormatInfo

Dim info As New DateTimeFormatInfo
info.PMDesignator = "N"

并将其作为IFormatProvider

提供给我的字符串格式化程序

trip.ArriveTime.ToString("hmmt", info)

但是我意识到设置DateTimeFormatInfo是静态的，当时间是12：00P或中午时没有任何用处。有没有办法创建一个能够解释这个独特场景的格式，并在中午时使用N后缀但是为其他时间保留标准A表示AM和P表示PM？

使用可能的解决方案进行更新：

Imports System.Text.RegularExpressions
Imports System.Globalization

Module mdlExtensions
    Private rgxTimePeriod As New Regex("t+")
    <System.Runtime.CompilerServices.Extension()> _
    Public Function LegacyFormat(dt As DateTime, fmt As String, Optional provider As IFormatProvider = Nothing) As String
        Dim formatted As String
        If dt.TimeOfDay = New TimeSpan(12, 0, 0) Then
            fmt = rgxTimePeriod.Replace(fmt, "N")
        End If
        If provider Is Nothing Then
            formatted = dt.ToString(fmt)
        Else
            formatted = dt.ToString(fmt, provider)
        End If

        Return formatted
    End Function

    <System.Runtime.CompilerServices.Extension()> _
    Public Function ToLegacy(dt As DateTime, fmt As String, Optional provider As IFormatProvider = Nothing) As String
        'setup the master DateTimeFormatInfo
        Dim ci As CultureInfo = CType(provider, CultureInfo)
        Dim mstrDtfi As DateTimeFormatInfo
        If provider Is Nothing Then
            'designate a new DateTimeFormatInfo class if Nothing was passed in
            mstrDtfi = New DateTimeFormatInfo
        Else
            'get a reference to the DateTimeFormatInfo class of the FormatProvider that was passed in
            mstrDtfi = ci.DateTimeFormat
        End If

        'check to see if the time is noon and set a new PMDesignator if it is
        If dt.TimeOfDay = New TimeSpan(12, 0, 0) Then
            mstrDtfi.PMDesignator = "NN"
        End If

        'check to see if the time is midnight and set a new AMDesignator if it is
        If dt.TimeOfDay = New TimeSpan(0, 0, 0) Then
            mstrDtfi.AMDesignator = "MM"
        End If

        'now format the date string with the proper provider 
        Dim formattedDate As String
        If provider Is Nothing Then
            formattedDate = dt.ToString(fmt, mstrDtfi)
        Else
            formattedDate = dt.ToString(fmt, ci)
        End If

        Return formattedDate
    End Function

End Module

Answer 1

我的目标是提供一种通用的解决方案，其格式可以像ddmm hhmmt或hmtt一样改变，并且重载会处理各种格式，除了＆＃34; t＆＃34;的特殊情况。说明符。

一个简单的函数仍然可以处理这个问题。这是一个扩展方法的例子。

Module Extensions
    Private rgxTimePeriod As New Regex("t+")
    <System.Runtime.CompilerServices.Extension()> _
    Public Function LegacyFmt(dt As DateTime, fmt As String, Optional provider As IFormatProvider = Nothing) As String
        Dim formatted As String
        If dt.TimeOfDay = New TimeSpan(12, 0, 0) Then
            fmt = rgxTimePeriod.Replace(fmt, "N")
        End If
        If provider Is Nothing Then
            formatted = dt.ToString(fmt)
        Else
            formatted = dt.ToString(fmt, provider)
        End If
        Return formatted
    End Function
End Module

?#12:00#.LegacyFmt("hmmt", Globalization.CultureInfo.InvariantCulture)
"1200N"
?now.LegacyFmt("ddmm")
"2551"
?#2:01#.LegacyFmt("hmmt")
?#12:00#.LegacyFmt("hmtt")
"120N"
"201A"
?#2:01#.LegacyFmt("hmtt")
"21AM"

AM / PM设计中午和午夜的特殊情况

1 个答案: