Setting response properties

gistfile1.cs

        static Dictionary<int, string> etags = new Dictionary<int, string>();

        // GET api/site/5
        public HttpResponseMessage Get(int id, HttpRequestMessage request)
        {
            var etag = request.Headers.IfNoneMatch; // strange that we can't do FirstOrDefault()

            if (etag != null && etags.ContainsKey(id))
            {
                if (etags[id] == etag.ToString())
                {
                    var notModified = new HttpResponseMessage(HttpStatusCode.NotModified);
                    return notModified;
                }
            }
            
            var site = session.Load<Site>(id);

            if (site == null || site.Deleted)
                ThrowSiteNotFound();

            var metadata = session.Advanced.GetMetadataFor(site);
            var siteEtag = metadata.Value<string>("@etag");

            etags[id] = siteEtag;

            var response = Request.CreateResponse<Site>(HttpStatusCode.OK, site);
            response.Headers.ETag = new EntityTagHeaderValue("\"" + siteEtag + "\"");
            response.Content.Headers.LastModified = metadata.Value<DateTime>("Last-Modified");

            return response;
        }

I'll have a look at CacheCow

no, not currently. Message Handler pipeline doesn't look for dependencies through DI.

Bu you can grab the the dependency inside a message handler as shown below:

protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) {

    var dependencyScope = request.GetDependencyScope();
    var service = dependencyScope.GetService(typeof(?));

    return base.SendAsync(request, cancellationToken);
}

Okay. Good to know. I've just added CacheCow as suggested and this looks like it will be much easier.