TcpClient EndRead event not setting class variable even with SyncLock

[cjelec]

Hi,

I'm having some trouble with Raising an event in a EndRead callback which is not setting a class variable even though I'm using SyncLock?

TCP class:

Private Sub StartReader()
   _stream.BeginRead(_read_buffer, 0, _read_buffer.Length, New AsyncCallback(AddressOf ReturnReader), _parent)
End Sub

Private Sub ReturnReader(res As IAsyncResult)

   _read_buffer_length = _stream.EndRead(res)

   'The code to get the data from the buffer and store it into a larger buffer works fine
   '...

   RaiseEvent OnDataReceivedEvent(me)

End Sub

Connection Handler Class (server):

Private WithEvents _tcp As TCP
Private _user As User 'Class containing user details
Private _loggedin As Boolean
Private _lock As Object = New Object()

Public Sub New()

   _user = New User()

End Sub

Private Sub OnDataReceived(Sender As Object) Handles _tcp.OnDataReceivedEvent
   'Gets here fine, except _user is always the same as when the class was created
   
   Dim Username As String
   Dim Command As String
   
   Command = _tcp.ReadLine()
   'Simplified for this example

   If GetCommand(Command) = "username" Then
      Username = GetValue(Command)

      'Two ways I have tried this:

      'First:
      SyncLock _user
          _user = New User(Username)
      End SyncLock

      'Second way without setting the _user in the Sub New:
      SyncLock _lock
          _user = New User(Username)
      End SyncLock

   Else GetCommand(Command) = "password" Then

      '_user is still the blank one or is nothing if I don't set it in the Sub New
      Dim logged As Boolean

      SyncLock _user
          logged = _user.CheckPassword(GetValue(Command))
      End SyncLock

      If logged = True Then
         SyncLock _lock
            _loggedin = True
         End SyncLock
      End If

   End If
End Sub

I have also tried the following and getting the same results:
- SyncLock me
- Inheriting the Tcp class and Overriding a Sub that is called in the ReturnReader Sub
- Using a Function in the User class that sets the user, so not creating a new instance of the User class
- Googling for over 6 hours

Please can someone help me?