VB.net Read Specific Lines From a Text File That Start With and Stop Reading When Start With - vb.net

Question

I'm looking to read lines from a text file that start with certain characters and stop when the line starts with other characters. So in my example I would like to start reading at line AB and stop at line EF however not all lines will contain the CD line. There will always be a AB line and EF line, however the number of lines in between is unknown.
Here is an example of the lines in a text file I would be reading. You can see that this will create two rows in the DataGridView however the first row is missing the CD line and should be blank.
AB-id1
EF-address1
AB-id2
CD-name1
EF-address2
Here is the code I have so far:
Dim lines() As String = File.ReadAllLines(textfile)
For i As Integer = 0 To lines.Length - 1
If lines(i).StartsWith("AB") Then
Dim nextLines As String() = lines.Skip(i + 1).ToArray
Dim info As String = nextLines.FirstOrDefault(Function(Line) Line.StartsWith("CD"))
Dim name As String = "Yes"
Dim info2 As String = nextLines.FirstOrDefault(Function(Line) Line.StartsWith("EF"))
Dim address As String = "Yes"
End If
DataGridView.Rows.Add(name,address)
Next
Now the output I currently get is:
|Yes|Yes|
|Yes|Yes|
And I should be getting:
||Yes|
|Yes|Yes|
It looks like it's reading too far down the text file and I need it to stop reading at EF. I've tried Do while and Do Until with no success. Any suggestions?

Answer 1

You could use the Array.FindIndex function to get the index of the next line starting with your prefix. This way you don't have to skip lines and create a new array each time.
Try this out instead:
Dim lines() As String = File.ReadAllLines(textFile)
For i As Integer = 0 To lines.Length - 1
If lines(i).StartsWith("AB") Then
Dim addressIndex As Integer = Array.FindIndex(lines, i + 1, Function(Line) Line.StartsWith("EF"))
Dim address As String = If(addressIndex <> -1, lines(addressIndex).Substring(3), "") ' Get everything past the "-"
Dim name As String = ""
If addressIndex <> -1 Then
Dim nameIndex As Integer = Array.FindIndex(lines, i + 1, addressIndex - i, Function(line) line.StartsWith("CD"))
If nameIndex <> -1 Then
name = lines(nameIndex).Substring(3) ' Get everything past the "-"
End If
End If
DataGridView.Rows.Add(name, address)
End If
Next