Scansionare rete lan con dominio

try
{
    IPHostEntry ipEntry = Dns.GetHostByName("NomeHost");
    IPAddress[] addr = ipEntry.AddressList;

    for (int i = 0; i < addr.Length; i++)
    {
        MessageBox.Show(String.Format("Indirizzo IP {0}: {1} ", i, addr[i].ToString()));
    }
}
catch (Exception ex)
{
    // Host sconosciuto.
    MessageBox.Show(ex.Message);
}

Function ElencoPC(ByVal dominio As String) As String()
    Dim dirs, dir As DirectoryEntry
    Dim Buffer(-1) As String
    Dim risp As New StringCollection
    Try
        dirs = New DirectoryEntry("WinNT://" & dominio)
        For Each dir In dirs.Children
            If dir.SchemaClassName = "Computer" Then
                risp.Add(dir.Name)
            End If
        Next

        If risp.Count > 0 Then
            ReDim Buffer(risp.Count - 1)
            risp.CopyTo(Buffer, 0)
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try

    Return Buffer
End Function

Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
    For Each pc As String In ElencoPC(txtDominio.Text)
        Dim ip As String = ""

        Try
            Dim ipEntry As IPHostEntry = Dns.GetHostByName(pc)
            Dim addr As IPAddress() = ipEntry.AddressList
            For i As Integer = 0 To addr.Count - 1
                ip &= vbCrLf & addr(i).ToString()
            Next
        Catch ex As Exception

        End Try
        MsgBox(pc & " :" & ip)
    Next
End Sub