The main thing that we have to focus is to override the QueryAccessToken method to use json response.
protected override string QueryAccessToken(Uri returnUrl, string authorizationCode)
{
var uri = BuildUri(TokenEndpoint, new NameValueCollection
{
{ "code", authorizationCode },
{ "client_id", _appId },
{ "client_secret", _appSecret },
{ "redirect_uri", returnUrl.GetLeftPart(UriPartial.Path) },
});
var webRequest = (HttpWebRequest)WebRequest.Create(uri);
string accessToken = null;
HttpWebResponse response = (HttpWebResponse)webRequest.GetResponse();
// handle response from FB
// this will not be a url with params like the first request to get the 'code'
Encoding rEncoding = Encoding.GetEncoding(response.CharacterSet);
using (StreamReader sr = new StreamReader(response.GetResponseStream(), rEncoding))
{
var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
var jsonObject = serializer.DeserializeObject(sr.ReadToEnd());
var jConvert = JsonConvert.DeserializeObject(JsonConvert.SerializeObject(jsonObject));
Dictionary<string, object> desirializedJsonObject = JsonConvert.DeserializeObject<Dictionary<string, object>>(jConvert.ToString());
accessToken = desirializedJsonObject["access_token"].ToString();
}
return accessToken;
}
I have replied the whole article/solution at this below link
http://stackoverflow.com/questions/43094777/facebookapplication-verifyauthentication-httpcontext-generatelocalcallbackuri/43303067#43303067