Imports System

Imports System.Text.RegularExpressions

Public Module Module1

    Public Sub Main()

        Dim data As String = "[Name=John][Last Name=xxx_xxx][Address=xxxx][Age=22][Phone Number=8454845]"

        Dim exp As String = "[[[]Last Name=(?<LastName>[^]]+)]"

        Console.WriteLine(RegEx.Match(data, exp).Groups("LastName").Value)

    End Sub

End Module