Get a custom attribute value from a server side extension

Hi

I am trying to extend my RTC with an OperationAdvisor .

My concern is to force user to fill a given custom attribute when the state is "Resolved" (close state) and the Resolution value is "Fixed Upstream"

1. is there a way to compare state and resolution to real string values ("Resolved" and "Fixed Upstream") and not to their identifier (state.s5 and resolution.r1)

2. how can I get a custom field value (check if not null) from server side.

I saw fews samples but I did not understand how to access workitem.attribute method from server side.

I appreciate a detailed example

Thx

Roger