HttpWebRequest Problem

[lowbird]

Hallo liebe Gemeinde

Ich versuche mir gerade einen "SteamAccount - Checker" zu basteln
Leider wird immer "Login Falsch" ausgegeben. Kann mir vielleicht jemand sagen
was ich falsch mache ?

Vielen Dank

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load


        Dim Username As String = "MySteamAcc"
        Dim Passwort As String = "MyPassword"

        Dim req As HttpWebRequest = WebRequest.Create("https://store.steampowered.com/login/index.php")
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
        req.Credentials = New NetworkCredential(Username, Passwort)
        req.PreAuthenticate = True
        req.Pipelined = False
        req.KeepAlive = True
        req.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6"
        req.UnsafeAuthenticatedConnectionSharing = False


        Dim Post As String = "redir=&username=" & Username & "&password=" & Passwort
        Dim res As HttpWebResponse = req.GetResponse()
        Dim reader As StreamReader = New StreamReader(res.GetResponseStream())
        Dim str As String = reader.ReadToEnd()

        If (str.Contains("logout")) Then
            MsgBox("Login geht")
        Else
            MsgBox("Login geht nicht")
        End If

    End Sub