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如何在SSIS VBScript中指定EOF?

script-component streamreader ssis vb.net sql-server

0

thursdaysgeek · 技术社区 · 16 年前

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:我实际上是想得到文件中最后一行的值。因此,读取到not EOF与读取到文件末尾并不完全相同。但是我剪的太多了,所以我的示例代码很差。

2 回复 | 直到 16 年前

1

Cade Roux 16 年前

从…起 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

如果您只需要最后一行:

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

2

1

Ray Dai 15 年前

它转到文件的末尾并开始向后读取,直到它碰到另一个LF字符,这表示从第二行到最后一行的末尾,然后它只读取该行。

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。

    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