在 ASP.NET 中打开/写入文本文件时出现问题

发布于 2024-07-15 03:29:15 字数 528 浏览 8 评论 0原文

我想在每次有人加载页面时将一些统计信息写入文本文件。但每隔一段时间我就会遇到“无法打开文件，已在使用”类型的错误。我不能 100% 复制这个错误，它非常不稳定。我的代码是

Public Sub WriteStats(ByVal ad_id As Integer)
    Dim ad_date As String = Now.Year & Now.Month

    Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
    Dim objStreamWriter As StreamWriter
    objStreamWriter = File.AppendText(FILENAME)
    objStreamWriter.WriteLine(ad_id & ";" & ad_date)
    objStreamWriter.Close()
End Sub

我的问题是，如何锁定和解锁文件，以便停止出现不稳定的错误？

谢谢

原文

I want to write some stats to a text file every time a person loads a page. But every once in awhile I am getting at 'Could Not Open File, Already in use' type of error. I can not 100% replicate this error it is very erratic. My code is

Public Sub WriteStats(ByVal ad_id As Integer)
    Dim ad_date As String = Now.Year & Now.Month

    Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
    Dim objStreamWriter As StreamWriter
    objStreamWriter = File.AppendText(FILENAME)
    objStreamWriter.WriteLine(ad_id & ";" & ad_date)
    objStreamWriter.Close()
End Sub

My question is, how can I lock and unlock the file so I stop getting the erratic errors?

Thanks

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呢古 2024-07-22 03:29:15

如果两个或多个请求大致同时到达您的网络服务器，它们都会尝试打开同一个文件。您需要为每个请求创建唯一的文件名。

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江湖彼岸 2024-07-22 03:29:15

Public Sub WriteStats(ByVal ad_id As Integer)
    Dim ad_date As String = Now.Year & Now.Month
    Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
    Dim index As Integer

    Using fs As New IO.FileStream(FILENAME, IO.FileMode.Append, IO.FileAccess.Write, IO.FileShare.ReadWrite), _
          tl As New TextWriterTraceListener(fs)

        index = Trace.Listeners.Add(tl)
        Trace.WriteLine(ad_id & ";" & ad_date)
        Trace.Listeners(index).Flush()
        Trace.Flush()
    End Using
    Trace.Listeners.RemoveAt(index)
End Sub

这里有三件重要的事情：

使用 IO.FileShare.ReadWrite 允许多个写入者同时写入文件。
即使发生异常，Using 语句也能确保立即关闭流。这将最大限度地减少冲突。
如果 TextWriterTraceListener 无法打开您请求的文件，它将为您创建一个临时文件，以确保消息不会丢失。

Public Sub WriteStats(ByVal ad_id As Integer)
    Dim ad_date As String = Now.Year & Now.Month
    Dim FILENAME As String = Server.MapPath("text/BoxedAds.txt")
    Dim index As Integer

    Using fs As New IO.FileStream(FILENAME, IO.FileMode.Append, IO.FileAccess.Write, IO.FileShare.ReadWrite), _
          tl As New TextWriterTraceListener(fs)

        index = Trace.Listeners.Add(tl)
        Trace.WriteLine(ad_id & ";" & ad_date)
        Trace.Listeners(index).Flush()
        Trace.Flush()
    End Using
    Trace.Listeners.RemoveAt(index)
End Sub

Three important things here:

Use of IO.FileShare.ReadWrite to allow multiple writers on the file at once.
The Using statement to make sure the stream is closed immediately, even if an exception occurs. This will minimize collisions
The TextWriterTraceListener will create a temp file for your if it can't open the file you request, to make sure the message isn't lost.

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