Facebook.FacebookClient.GetException C# (CSharp) Method

        internal static Exception GetException(HttpHelper httpHelper, object result)
        {
            if (result == null)
                return null;

            var responseDict = result as IDictionary<string, object>;
            if (responseDict == null)
                return null;

            FacebookApiException resultException = null;

            if (httpHelper != null)
            {
                var response = httpHelper.HttpWebResponse;
                var responseUri = response.ResponseUri;

                // legacy rest api
                if (responseUri.Host == "api.facebook.com" ||
                    responseUri.Host == "api-read.facebook.com" ||
                    responseUri.Host == "api-video.facebook.com" ||
                    responseUri.Host == "api.beta.facebook.com" ||
                    responseUri.Host == "api-read.beta.facebook.com" ||
                    responseUri.Host == "api-video.facebook.com")
                {
                    if (responseDict.ContainsKey("error_code"))
                    {
                        string errorCode = responseDict["error_code"].ToString();
                        string errorMsg = null;
                        if (responseDict.ContainsKey("error_msg"))
                            errorMsg = responseDict["error_msg"] as string;

                        // Error Details: http://wiki.developers.facebook.com/index.php/Error_codes
                        if (errorCode == "190")
                            resultException = new FacebookOAuthException(errorMsg, errorCode);
                        else if (errorCode == "4" || errorCode == "API_EC_TOO_MANY_CALLS" ||
                                 (errorMsg != null && errorMsg.Contains("request limit reached")))
                            resultException = new FacebookApiLimitException(errorMsg, errorCode);
                        else
                            resultException = new FacebookApiException(errorMsg, errorCode);
                        return resultException;
                    }

                    return null;
                }
            }

            // graph api error
            if (responseDict.ContainsKey("error"))
            {
                var error = responseDict["error"] as IDictionary<string, object>;
                if (error != null)
                {
                    var errorType = error["type"] as string;
                    var errorMessage = error["message"] as string;
                    int errorCode = 0;

                    if (error.ContainsKey("code"))
                        int.TryParse(error["code"].ToString(), out errorCode);

                    var errorSubcode = 0;
                    if (error.ContainsKey("error_subcode"))
                        int.TryParse(error["error_subcode"].ToString(), out errorSubcode);

                    string errorUserTitle = null;
                    if (error.ContainsKey("error_user_title"))
                        errorUserTitle = (string)error["error_user_title"];

                    string errorUserMsg = null;
                    if (error.ContainsKey("error_user_msg"))
                        errorUserMsg = (string)error["error_user_msg"];

                    // Check to make sure the correct data is in the response
                    if (!string.IsNullOrEmpty(errorType) && !string.IsNullOrEmpty(errorMessage))
                    {
                        // We don't include the inner exception because it is not needed and is always a WebException.
                        // It is easier to understand the error if we use Facebook's error message.
                        if (errorType == "OAuthException")
                            resultException = new FacebookOAuthException(errorMessage, errorType, errorCode, errorSubcode);
                        else if (errorType == "API_EC_TOO_MANY_CALLS" || (errorMessage.Contains("request limit reached")))
                            resultException = new FacebookApiLimitException(errorMessage, errorType);
                        else
                            resultException = new FacebookApiException(errorMessage, errorType, errorCode, errorSubcode);
                    }

                    resultException.ErrorUserTitle = errorUserTitle;
                    resultException.ErrorUserMsg = errorUserMsg;
                }
                else
                {
                    long? errorNumber = null;
                    if (responseDict["error"] is long)
                        errorNumber = (long)responseDict["error"];
                    if (errorNumber == null && responseDict["error"] is int)
                        errorNumber = (int)responseDict["error"];
                    string errorDescription = null;
                    if (responseDict.ContainsKey("error_description"))
                        errorDescription = responseDict["error_description"] as string;
                    if (errorNumber != null && !string.IsNullOrEmpty(errorDescription))
                    {
                        if (errorNumber == 190)
                            resultException = new FacebookOAuthException(errorDescription, "API_EC_PARAM_ACCESS_TOKEN");
                        else
                            resultException = new FacebookApiException(errorDescription, errorNumber.Value.ToString(CultureInfo.InvariantCulture));
                    }
                }
            }

            return resultException;
        }