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在 SSIS VBScript 中读取直到文件结尾的语法是什么？

Dim readFile As FileInfo = New FileInfo(logHourlyName)
If readFile.Exists() Then
   Dim textStream As StreamReader = readFile.OpenText()
   Dim strLine As String
   Do While Not EOF    <--- what goes here?
       curLine = textStream.ReadLine()
   Loop
   textStream.Close()
End If

编辑：我实际上是在尝试获取文件中最后一行的值。因此，读取直到不是 EOF 与读取到文件末尾并不完全相同。但是我删减了很多，以至于我的示例代码很差。

4

2 回答 2

1

来自http://msdn.microsoft.com/en-us/library/system.io.streamreader.aspx：

Dim readFile As FileInfo = New FileInfo(logHourlyName)
If readFile.Exists() Then
   Dim textStream As StreamReader = readFile.OpenText()
   Dim strLine As String
   Do
       curLine = textStream.ReadLine()
   Loop Until curLine Is Nothing
   textStream.Close()
End If

如果你只想要最后一行：

Dim readFile As FileInfo = New FileInfo(logHourlyName)
Dim lastLine As String
If readFile.Exists() Then
   Dim textStream As StreamReader = readFile.OpenText()
   Dim strLine As String
   Do
       curLine = textStream.ReadLine()
       If Not curLine Is Nothing Then lastLine = curLine
   Loop Until curLine Is Nothing
   textStream.Close()
End If
于 2009-01-29T00:18:19.317 回答
1

这是一种只读取最后一行而不遍历整个文件的方法。它走到文件的末尾并开始向后读取，直到遇到另一个 LF 字符，这表示倒数第二行的结尾，然后它只是读入该行。

在具有数百万行的大文件上，这降低了读取几个字节的成本。

您可以取消注释 Dts.Events.FireInformation 代码在输出窗口中发生的事情。

    Dim i As Integer
    Dim CurrentByte As Integer
    Dim Trailer As String

    i = 1

    Using reader As StreamReader = New StreamReader("c:\temp\SourceFile.txt")
        Do While CurrentByte <> 10 'while we are not finding the next LF character
           reader.BaseStream.Seek((-1 * i) - 2, SeekOrigin.End) 'seeking backwards from the last position in the file minus the last CRLF
            'Dts.Events.FireInformation(0, "Now at position", reader.BaseStream.Position().ToString, "", 0, False)
            CurrentByte = reader.BaseStream.ReadByte 'read the next byte, this will advance pointer position
            'Dts.Events.FireInformation(0, "Current ASCII Code", CurrentByte & " Character:" & Chr(CurrentByte), "", 0, False)
            i = i + 1 'go to the next character                 
        Loop
        Trailer = reader.ReadLine 'we exited on the LF character, so we are at the beginning of trailer line
        Dts.Events.FireInformation(0, "   Trailer:", Trailer, "", 0, False)
    End Using
于 2009-12-30T19:25:50.010 回答