逐行读取文本以进行字符串操作

Question

因此，这是我已经编写的代码：

        Dim MyFile As String = "Path"
        Dim str_new As String
        Dim str_old As String = File.ReadAllText(MyFile)

        Dim sr As New StreamReader(MyFile)
        Dim strLines As String() = Strings.Split(sr.ReadToEnd, Environment.NewLine)
        Dim Character As Integer = 5 'Line 1 always has 5 characters
        For i = 2 To strLines.Length
            Dim PreviousLine As String = sr.ReadLine(i - 1)
            Dim CurrentLine As String = sr.ReadLine(i)
            If CurrentLine.Contains(TextBox1.Text / 100) Then
                If PreviousLine.Contains("divide") Then
                    Exit For
                End If
            End If
            Character = Character + CurrentLine.Length
        Next
        sr.Close()

        str_new = Replace(str_old, (TextBox1.Text / 100), (TextBox3.Text / 100), Character, 1)

            Dim objWriter3 As New System.IO.StreamWriter(MyFile, False)
            objWriter3.Write(str_new)
            objWriter3.Flush()
            objWriter3.Close()

我正在尝试找出一种方法将长代码文件分成几行，然后检查每一行是否有某些字符串。如果当前行包含字符串，那么我将对上面和/或下面的行进行额外检查，以确保这是字符串的正确实例。最后，我想用不同的字符串替换字符串的那个实例。

一个例子：文本文件

class
...
0.3
divide   <-- Previous Line
0.3     <-- TextBox1.Text is 30
.5
end

1. 我希望代码超过 0.3 的第一个实例
2. 找到第二个实例
3. 检查上一行是否有除法
4. 退出循环
5. 将 0.3 的第二个实例替换为某个值

我已经对此进行了一段时间的研究，我们将不胜感激任何帮助！ ~马特

修订：代码

        Dim MyFile As String = "Path"
        Dim NewFile As String = "Temporary Path"
        Dim PreviousLine As String = ""
        Dim CurrentLine As String = ""
        Using sr As StreamReader = New StreamReader(MyFile)
            Using sw As StreamWriter = New StreamWriter(NewFile)
                CurrentLine = sr.ReadLine
                Do While (Not CurrentLine Is Nothing)
                    Dim LinetoWrite = CurrentLine

                    If CurrentLine.Contains(TextBox1.Text) Then
                        If PreviousLine.Contains("divide") Then
                            LinetoWrite = Replace(CurrentLine, TextBox1.Text, TextBox3.Text)
                        End If
                    End If

                    sw.WriteLine(LinetoWrite)
                    PreviousLine = CurrentLine
                    CurrentLine = sr.ReadLine
                Loop
            End Using
        End Using

        My.Computer.FileSystem.CopyFile(NewFile, MyFile, True)

Answer 1

您以错误的方式面对问题。您必须同时设置读取器和写入器，并生成一个包含所有修改的新文件。您的代码有很多需要改进的部分；在这个答案中，我只是展示如何正确使用StreamReader/StreamWriter。示例代码：

Dim MyFile As String = "input path"
Dim OutputFile As String = "output path"
Dim PreviousLine As String = ""
Dim CurrentLine As String = ""
Using sr As StreamReader = New StreamReader(MyFile)
    Using sw As StreamWriter = New StreamWriter(OutputFile)

        CurrentLine = sr.ReadLine

        Do While (Not CurrentLine Is Nothing)

            Dim lineToWrite = CurrentLine

            'Perform the analysis you wish by involving the current line, the previous one and as many other (previous) lines as you wish; and store the changes in lineToWrite. You should call a function here to perform this analysis

            sw.WriteLine(lineToWrite) 'Writing lineToWrite to the new file

            PreviousLine = CurrentLine 'Future previous line
            CurrentLine = sr.ReadLine 'Reading the line for the next iteration
        Loop
    End Using
End Using