Difference between the two Web API headers response.Content.Headers and response.Headers

Question

I find WebAPI separate HTTP response headers into different places, one is in Response.Headers, the other in in Response.Content.Headers. For example, etag is in Response.Headers while lastModified is in the other. What is the reason behind that?

Answer 1

There are a couple of answers to that question. One is because that's the way the HTTP spec defines the headers.

RFC 2616

• Content header fields here https://www.rfc-editor.org/rfc/rfc2616#section-7.1
• Request header fields here https://www.rfc-editor.org/rfc/rfc2616#section-5.3
• Response header fields here https://www.rfc-editor.org/rfc/rfc2616#section-6.2

The other more practical reason for separating out the content headers is that it is easier write code that processes data into HTTP payloads and sets the related headers, independent of the request/response objects.

Unfortunately, the more recent HTTPbis specification did some reorganization of where they think headers should go and now LastModified and Allow are considered response fields, not content fields. This means that the headers as defined in System.Net.HttpHeaders will no longer match the spec, which really sucks. It also means that we are probably stuck with LastModified as a HttpContent header and Etag as a response header.

HTTPbis

• Content related headers are defined here.
• Request headers here.
• Response headers here.