Select text between key words - vb.net

Question

This is a follow on question to Select block of text and merge into new document
I have a SGM document with comments added and comments in my sgm file. I need to extract the strings in between the start/stop comments so I can put them in a temporary file for modification. Right now it's selecting everything including the start/stop comments and data outside of the start/stop comments.
Dim DirFolder As String = txtDirectory.Text
Dim Directory As New IO.DirectoryInfo(DirFolder)
Dim allFiles As IO.FileInfo() = Directory.GetFiles("*.sgm")
Dim singleFile As IO.FileInfo
Dim Prefix As String
Dim newMasterFilePath As String
Dim masterFileName As String
Dim newMasterFileName As String
Dim startMark As String = "<!--#start#-->"
Dim stopMark As String = "<!--#stop#-->"
searchDir = txtDirectory.Text
Prefix = txtBxUnique.Text
For Each singleFile In allFiles
If File.Exists(singleFile.FullName) Then
Dim fileName = singleFile.FullName
Debug.Print("file name : " & fileName)
' A backup first
Dim backup As String = fileName & ".bak"
File.Copy(fileName, backup, True)
' Load lines from the source file in memory
Dim lines() As String = File.ReadAllLines(backup)
' Now re-create the source file and start writing lines inside a block
' Evaluate all the lines in the file.
' Set insideBlock to false
Dim insideBlock As Boolean = False
Using sw As StreamWriter = File.CreateText(backup)
For Each line As String In lines
If line = startMark Then
' start writing at the line below
insideBlock = True
' Evaluate if the next line is <!Stop>
ElseIf line = stopMark Then
' Stop writing
insideBlock = False
ElseIf insideBlock = True Then
' Write the current line in the block
sw.WriteLine(line)
End If
Next
End Using
End If
Next
This is the example text to test on.
<chapter id="Chapter_Overview"> <?Pub Lcl _divid="500" _parentid="0">
<title>Learning how to gather data</title>
<!--#start#-->
<section>
<title>ALTERNATE MISSION EQUIPMENT</title>
<para0 verdate="18 Jan 2019" verstatus="ver">
<title>
<applicabil applicref="xxx">
</applicabil>Three-Button Trackball Mouse</title>
<para>This is the example to grab all text between start and stop comments.
</para></para0>
</section>
<!--#stop#-->
Things to note: the start and stop comments ALWAYS fall on a new line, a document can have multiple start/stop sections
I thought maybe using a regex on this
(<section>[\w+\w]+.*?<\/section>)\R(<\?Pub _gtinsert.*>\R<pgbrk pgnum.*?>\R<\?Pub /_gtinsert>)*
Or maybe use IndexOf and LastIndexOf, but I couldn't get that working.

Answer 1

You can read the entire file and split it into an array using the string array of {"<!--#start#-->", "<!--#stop#-->"} to split, into this
Element 0: Text before "<!--#start#-->"
Element 1: Text between "<!--#start#-->" and "<!--#stop#-->"
Element 2: Text after "<!--#stop#-->"
and take element 1. Then write it to your backup.
Dim text = File.ReadAllText(backup).Split({startMark, stopMark}, StringSplitOptions.RemoveEmptyEntries)(1)
Using sw As StreamWriter = File.CreateText(backup)
sw.Write(text)
End Using
Edit to address comment
I did make the original code a little compact. It can be expanded out into the following, which allows you to add some validation
Dim text = File.ReadAllText(backup)
Dim split = text.Split({startMark, stopMark}, StringSplitOptions.RemoveEmptyEntries)
If split.Count() <> 3 Then Throw New Exception("File didn't contain one or more delimiters.")
text = split(1)
Using sw As StreamWriter = File.CreateText(backup)
sw.Write(text)
End Using