how to parse the SFSObject from the paramemter(smartfox server))

I send a message with SFSObject to smartfox server

void public SendMessageToOther(SFSObject dataObj) {

Room room = smartFox.LastJoinedRoom;

 smartFox.Send(new PublicMessageRequest(dataObj.GetUtfString("type").ToString()+":"+dataObj.GetFloat("PositionIdx").ToString(),dataObj));
     
 }

when I use the following script to parse the response data. I get message from parameter but I cant parse the SFSObject from the parameter

void OnPublicMessage(BaseEvent evt) { try { string message = (string)evt.Params["message"]; User sender = (User)evt.Params["sender"];

         // We use lock here to ensure cross-thread safety on the messages collection 
         lock (messagesLocker) {
             messages.Add(sender.Name + " said " + message);
         }
          ISFSObject dt = (SFSObject)evt.Params["params"];

}

How can I get the ISFSObject of the parameter?