Imports System
Imports System.Text.RegularExpressions
 
Public Class Test
    Public Shared Sub Main()
        Dim FileLines() As String = New String() {"test", "I am a line", "cool:", "username: Hello123", "Username: John", "Hello there", "USERnaMe: J.Johnsson", "test again"}
 
        Console.WriteLine("--- Input lines ---")
 
        For Each InputLine As String In FileLines
            Console.WriteLine(InputLine)
        Next
 
        Console.WriteLine(Environment.NewLine & "--- Found usernames ---")
 
        Dim RgEx As New Regex("(?<=username:\s).+", RegexOptions.IgnoreCase) 'Declare a new, case-insensitive Regex.
        For Each Line As String In FileLines
            Dim m As Match = RgEx.Match(Line)
            If m IsNot Nothing AndAlso m.Success = True Then
                Console.WriteLine(m.Value)
            End If
        Next
    End Sub
End Class

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