How can I use this code?

TextBox1.Text = Array.FindIndex(linestring, Function(s) s.Contains(something))

but to use the code, without a word, and to display my array index following the code below:

Dim lines As New List(Of String)
    
Using reader As New StreamReader(My.Application.Info.DirectoryPath   ("\Data.txt"))
    
    Dim line As String
    
    Do Until line.StartsWith(endPrefix)

        lines.Add(line)
        line = reader.ReadLine()

        'maybe here index of array 

    Loop

so how do I use this to get the line index from my text files?

CodePudding user response：

Here is an example which uses the File.ReadLines method (which enumerates the lines of a file) where you can pass the predicate for the comparison to get the line number (starting at 1) of the first match:

Imports System.IO

Module Module1

    Function FindLineNumber(sourceFile As String, textToFind As String, predicate As Func(Of String, String, Boolean)) As Integer
        Dim lineNo = 1

        For Each l In File.ReadLines(sourceFile)
            If predicate(l, textToFind) Then
                Return lineNo
            End If
            lineNo  = 1
        Next

        Return -1

    End Function

    Sub Main()
        ' File to look in:
        Dim src = "C:\temp\population.csv"
        ' Text to find:
        Dim find = "133"

        Dim lineNum = FindLineNumber(src, find, Function(a, b) a.Contains(b))

        If lineNum > 0 Then
            Console.WriteLine($"""{find}"" found at line {lineNum}.")
        Else
            Console.WriteLine($"""{find}"" not found.")
        End If

        Console.ReadLine()

    End Sub

End Module