将字符串转换为日期

Question

这是为了我的VB.Net项目。在这一阶段，我将数据从excel拉到VS2010。

在此我有字符串格式为25.10.2013的日期，我想在datagrid中添加此日期，但它显示"Conversion from string "“25.10.2013”to type ' date‘is not valid“错误。

请检查以下两个编码(函数和While)，并为我提供解决方案来解决这个问题。

If DialogResult = Windows.Forms.DialogResult.OK Then
  Try
    Dim objreader As New System.IO.StreamReader(OpenDLG.FileName)
    linecount = 0
    dupord = 0
    nooford = 0

    While Not objreader.EndOfStream
        fallout = objreader.ReadLine
        If linecount >= 0 Then
          If fallout = "" Then
              Exit While
          End If
        ' Dim tmpArray() As String = Regex.Split(Trim(velocityfallout), " ")
          Dim tmpArray() As String = Regex.Split(Trim(fallout), ",")
          If tmpArray(0) = "" Then
            Exit While
          End If
          pono = tmpArray(0)
          issue = tmpArray(1)
          falldate = getToday(tmpArray(3))
          ftype = "Velocity"
          checkfallout("Velocity", "", "", falldate, "", pono, "", issue, "")
          nooford = nooford + 1

       End If
      linecount += 1
    End While

GetToday函数：

Function getToday(ByVal dateStr As Date) As String

    Dim dateStrRet As String

    dateStrRet = CStr(DatePart("yyyy", dateStr)) & "-"

    If DatePart("m", dateStr) < 10 Then
        dateStrRet = dateStrRet & "0" & CStr(DatePart("m", dateStr)) & "-"
    Else
        dateStrRet = dateStrRet & CStr(DatePart("m", dateStr)) & "-"
    End If

    If DatePart("d", dateStr) < 10 Then
        dateStrRet = dateStrRet & "0" & CStr(DatePart("d", dateStr))
    Else
        dateStrRet = dateStrRet & CStr(DatePart("d", dateStr))
    End If

    Return dateStrRet
End Function

Answer 1

我假设方法getToday应该返回今天的日期字符串，您可以通过Date.Today.ToShortDateString或Date.Today.ToString("d")获得它。但是，如果您希望它采用特定的格式，例如使用英语或德语日期分隔符，则必须提供适当的IFormatProvider。例如，德国文化"de-DE"使用.作为日期分隔符：

'fallback culture
Private Shared ReadOnly deCulture As CultureInfo = CultureInfo.CreateSpecificCulture("de-DE")

Function getToday(ByVal dt As Date, Optional provider As IFormatProvider = Nothing) As String
    ' force culture "de-DE" (germany) if no one was provided:
    If provider Is Nothing Then provider = deCulture
    Return dt.ToString("d", provider)
End Function

由于它不是很清楚，也许您在从字符串中解析日期时也会遇到问题。然后，您必须使用具有适当区域性的Date.Parse或Date.ParseExact (或TryParse方法)：

Dim dateStr As String = tmpArray(3)
Dim deCulture As CultureInfo = CultureInfo.CreateSpecificCulture("de-DE")
Dim dt As Date
If Date.TryParse(dateStr, deCulture, DateTimeStyles.None, dt) Then
    dateStr = getToday(dt, deCulture) ' you can omit deCulture since that is default here
End If