The application I am writing interacts with OData service that supports ETags. I am going to cache data returned by the service and use ETags to determine whether that data has been modified since it was cached. To do this, I need to:

 - extract ETags from returned data;

- add ETags to subsequent requests;

- analyse response - if it is "304 - Not modified" (in this case, I will use cached data) or "200 - OK" (in this case, I will update local cache with new data returned in the response).

So, I have a few questions:

1. Is it possible to extract ETags from responses and then add them to subsequent requests?

2. Could you give me any advice about caching?