如何使用 vb.net 更新 CSV 文件以不插入新项目答案

【问题标题】：How to Update CSV file not to Insert new Items using vb.net如何使用 vb.net 更新 CSV 文件以不插入新项目
【发布时间】：2015-10-02 20:14:30
【问题描述】：

我想更新我尝试过的 CSV 文件的行，但我只找到了添加新行的 append。因为我需要更新行而不是插入新行。

这是我的 csv 文件中的数据

EnjoyBaseHid=hid://002AB1E3,MinID=1,MaxID=900 EnjoyBaseHid=hid://005AC1D4,MinID=1,MaxID=600

我要根据EnjoyBaseHid更新

While Not sr.EndOfStream
                            Dim line = sr.ReadLine()
                            Dim values() As String = line.Split(",")
                            If values(0).Equals("EnjoyBaseHid=" & portAddress) Then
                                Nobasefound = False
                                line = line.Replace(values(1), "MinID=" & minID)
                                line = line.Replace(values(2), "MaxID=" & maxID)
                                sr.Close()
                                Dim strWrite As New IO.StreamWriter(ExportListPathString, False)
                                strWrite.WriteLine(line)
                                strWrite.Close()
                                Exit While
                            End If
End While

这会覆盖所有文件，结果是

EnjoyBaseHid=hid://005AC1D4,MinID=1,MaxID=1000

当我更改以下行时

Dim strWrite As New IO.StreamWriter(ExportListPathString, False)

到这里

Dim strWrite As New IO.StreamWriter(ExportListPathString, True)

它追加新行，结果如下

EnjoyBaseHid=hid://002AB1E3,MinID=1,MaxID=900
EnjoyBaseHid=hid://005AC1D4,MinID=1,MaxID=600
EnjoyBaseHid=hid://005AC1D4,MinID=1,MaxID=1000

但我需要这个

EnjoyBaseHid=hid://002AB1E3,MinID=1,MaxID=900 EnjoyBaseHid=hid://005AC1D4,MinID=1,MaxID=1000

【问题讨论】：

两个流怎么样。一个读者和一个作家。从源文件中写入每一行，直到到达要插入新行的位置。然后写新行。通过编写源文件中的其余行来完成。
我同时使用流写入器和读取器 sr 是流读取器，strwrite 是流写入器，我不想插入新行我只想更新文件中存在的行

标签： vb.net streamreader streamwriter

【解决方案1】：

这是我的想法。

Private Sub fileHandler(sourceFile As String, portAddress As String, newMin As String, newMax As String)

    Dim tempOutFileName As String = String.Concat(sourceFile, "_tmp")
    Dim oldFileName As String = String.Concat(sourceFile, "_old")

    'clear away temp file
    If File.Exists(tempOutFileName) Then
        File.Delete(tempOutFileName)
    End If

    'clear away old file
    If File.Exists(oldFileName) Then
        File.Delete(oldFileName)
    End If

    'open writer for new temp file
    Using sw As StreamWriter = New StreamWriter(tempOutFileName, True)
        'open reader for source file
        Using sr As StreamReader = New StreamReader(sourceFile)
            Do While sr.Peek <> -1
                Dim line As String = sr.ReadLine
                'check if the line read is the one you want to change
                If line.Contains(portAddress) Then
                    'write your NEW line
                    sw.WriteLine(String.Concat(portAddress, "-", newMin, "-", newMax))
                Else
                    'write the existing line without changes
                    sw.WriteLine(line)
                End If
            Loop
            sr.Close()
        End Using
        sw.Close()
    End Using

    'backup source to old
    File.Move(sourceFile, oldFileName)
    'move temp to source
    File.Move(tempOutFileName, sourceFile)

End Sub

【讨论】：