Facebook-Login via Visual Basic POST

Imports System.Net
Imports System.Text
Imports System.IO

Public Class Form1
    Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
        Dim url_login As String = "https://www.facebook.com/login.php"  
        Dim username As String = "user@domain.de"  
        Dim password As String = "GaNzGeHeim"  
        Dim strPostData As String = "?email=" & username & "&pass=" & password  
        Dim strUserAgent As String = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0"  

        Dim cookies As New CookieContainer
        Dim postBytes() As Byte = Encoding.ASCII.GetBytes(strPostData)
        Dim request As HttpWebRequest = WebRequest.Create(url_login)

        With request
            .Method = "POST"  
            .ContentType = "application/x-www-form-urlencoded"  
            .UserAgent = strUserAgent
            .ContentLength = postBytes.Length
            .CookieContainer = cookies
            Dim stream As Stream
            stream = request.GetRequestStream()
            Using stream
                stream.Write(postBytes, 0, postBytes.Length)
                stream.Close()
            End Using
            .GetResponse()
        End With
        'Seite welche abgerufen werden soll nachdem der User eingeloggt ist  
        Dim pageRequest As HttpWebRequest = WebRequest.Create("https://www.facebook.com/pages")  
        With pageRequest
            .CookieContainer = cookies
            .UserAgent = strUserAgent
            .Method = "GET"  
            Dim stream As New StreamReader(pageRequest.GetResponse().GetResponseStream())
            Using stream
                'Quellcode der Seite in einer Textbox ablegen  
                txtWebpage.Text = stream.ReadToEnd()
                stream.Close()
            End Using
        End With
    End Sub
End Class