internal Func <HttpRequestMessage, Task <HttpResponseMessage> > GetIfMatchNoneMatch()
{
return((request) =>
{
if (request.Method != HttpMethod.Get)
{
return null;
}
ICollection <EntityTagHeaderValue> noneMatchTags = request.Headers.IfNoneMatch;
ICollection <EntityTagHeaderValue> matchTags = request.Headers.IfMatch;
if (matchTags.Count == 0 && noneMatchTags.Count == 0)
{
return null; // no etag
}
if (matchTags.Count > 0 && noneMatchTags.Count > 0) // both if-match and if-none-match exist
{
return new HttpResponseMessage(HttpStatusCode.BadRequest).ToTask();
}
bool isNoneMatch = noneMatchTags.Count > 0;
ICollection <EntityTagHeaderValue> etags = isNoneMatch ? noneMatchTags : matchTags;
string resource = UriTrimmer(request.RequestUri);
IEnumerable <KeyValuePair <string, IEnumerable <string> > > headers =
request.Headers.Where(h => _varyByHeaders.Any(v => v.Equals(h.Key, StringComparison.CurrentCultureIgnoreCase)));
EntityTagKey entityTagKey = EntityTagKeyGenerator(resource, headers);
// compare the Etag with the one in the cache
// do conditional get.
TimedEntityTagHeaderValue actualEtag = null;
bool matchFound = false;
if (_entityTagStore.TryGetValue(entityTagKey, out actualEtag))
{
if (etags.Any(etag => etag.Tag == actualEtag.Tag))
{
matchFound = true;
}
}
return matchFound ^ isNoneMatch ? null : new NotModifiedResponse(actualEtag.ToEntityTagHeaderValue()).ToTask();
});
}