Django Authentication from .NET using HttpWebRequest and HttpWebResponse via HTTP POST

I am creating an application in .NET that will serve as a second UI for my already-deployed Django app. For some operations users need to authenticate themselves (as Django users). I used a super-simple way to do this (without encrypting credentials for simplicity):-

Step 1. I created a django view that accepted the username and password through two HTTP GET parameters and passed them on to django.contrib.auth.authenticate() as keyword arguments. See the code below:

    def authentication_api(request, raw_1, raw_2):
        user = authenticate(username=raw_1, password=raw_2)
        if user is not None:
            if user.is_active:
                return HttpResponse("correct", mimetype="text/plain")
            else:
                return HttpResponse("disabled", mimetype="text/plain")
        else:
            return HttpResponse("incorrect", mimetype="text/plain")

Step 2. I called this using the following code in .NET. The 'strAuthURL' in the following representes a simple django URL mapped to the django view above:

    Dim request As HttpWebRequest = CType(WebRequest.Create(strAuthURL), HttpWebRequest)
    Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
    Dim reader As StreamReader = New StreamReader(response.GetResponseStream())
    Dim result As String = reader.ReadToEnd()
    HttpWResp.Close()

This works flawlessly, although it is nothing more than a proof-of-concept.

Now I want to do this via HTTP POST so I have done the following: -

I created a django view for the doing authentication using POST data

    def post_authentication_api(request):
        if request.method == 'POST':
            user = authenticate(username=request.POST['username'], password=request.POST['password'])
            if user is not None:
                if user.is_active:
                    return HttpResponse("correct", mimetype="text/plain")
                else:
                    return HttpResponse("disabled", mimetype="text/plain")
            else:
                return HttpResponse("incorrect", mimetype="text/plain")

I have tested this using restclient and this view works as expected. However I can't get it to work from the .NET code below:

    Dim request As HttpWebRequest = CType(WebRequest.Create(strAuthURL), HttpWebRequest)
    request.ContentType = "application/x-www-form-urlencoded"
    request.Method = "POST"
    Dim encoding As New UnicodeEncoding
    Dim postData As String = "username=" & m_username & "&password=" & m_password
    Dim postBytes As Byte() = encoding.GetBytes(postData)
    request.ContentLength = postBytes.Length
    Try
        Dim postStream As Stream = request.GetRequestStream()
        postStream.Write(postBytes, 0, postBytes.Length)
        postStream.Close()
        Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
        Dim responseStream As New StreamReader(response.GetResponseStream(), UnicodeEncoding.Unicode)
        result = responseStream.ReadToEnd()
        response.Close()
    Catch ex As Exception
        MessageBox.Show(ex.ToString)
    End Try

The server is giving me a 500 internal server error. My guess is that the POST request is not properly set up in .NET. So I basically need some guidance on how to call the django view from .NET sending POST data.

Thanks, CM