Http Validation with ETags

Is there any built-in help for managing HTTP Validation with ETags in headers in responses from a service?

I am looking some something general purpose that can easily be added, to generate the ETag on responses (given any response), and then something else to handle receiving ETag and If-None-Match header and sending 304-ContentNotModified.

No there isn’t, it’s hard to provide anything reusable functionality since it’s specific to each Service and can’t be calculated generically.