/**
* Return Authorization url to get auth_code
*
* @return string
*/
public string get_auth_url() {
_client = new Client();
string url = _client.get_dashboard_url() + "/auth";
var param = new { response_type = "code", client_id =_client.client_id , redirect_uri = _client.get_current_url(),scope=_client.scope };
url = _client.create_get_url(url, param);
return url;
}