You can override the MessageReceived(...) function of the LuisDialog keep the fields of the message that you need as member variables and access those fields in your intent handlers. Below I modified the SimpleAlarmDialog to show how you can access 'message.Text' in one of the intent handlers:
[LuisModel("c413b2ef-382c-45bd-8ff0-f76d60e2a821", "6d0966209c6e4f6b835ce34492f3e6d9")]
[Serializable]
public class SimpleAlarmDialog : LuisDialog