Binaryworld - CheckWindowsUser - Check whether a username/password pair is correct ... [ VB.net -> Windows ]

<System.Runtime.InteropServices.DllImport("advapi32")> Shared Function _
  LogonUser(ByVal userName As String, ByVal domain As String, _
  ByVal password As String, ByVal dwLogonType As Integer, _
  ByVal dwLogonProvider As Integer, ByRef phToken As Integer) As Integer
End Function

<System.Runtime.InteropServices.DllImport("kernel32")> Shared Function _
  CloseHandle(ByVal hObject As Integer) As Integer
End Function

' Check whether a username/password pair is correct
'
' if DOMAIN is omitted, it uses the local account database
' and then asks trusted domains to search their account databases
' until it finds the account or the search is exhausted
' use DOMAIN="." to search only the local account database
'
' IMPORTANT: works only under Windows NT and 2000

Function CheckWindowsUser(ByVal userName As String, ByVal password As String, _
  Optional ByVal domain As String = "") As Boolean
  Const LOGON32_PROVIDER_DEFAULT = 0&
  Const LOGON32_LOGON_NETWORK = 3&

  Dim hToken, ret As Integer

  ' provide a default for the Domain name
  'If domain.Length = 0 Then domain = Nothing
  ' check the username/password pair using LOGON32_LOGON_NETWORK delivers the
  ' best performance
  ret = LogonUser(userName, domain, password, LOGON32_LOGON_NETWORK, _
    LOGON32_PROVIDER_DEFAULT, hToken)
  ' a non-zero value means success
  If ret Then
    CheckWindowsUser = True
    CloseHandle(hToken)
  End If
End Function