Limitations

No synchronous requests

IHttpCacheStore is asynchronous, so there is no synchronous path through the cache. HttpClient.Send throws a NotSupportedException rather than sending the request to the server without caching it. Use SendAsync, GetAsync, PostAsync and the other asynchronous methods.

No request coalescing

The handler is thread-safe and can be used by concurrent requests. However, concurrent requests for a URL that is not stored yet each go to the server, and each stores its response: the last one written wins. To send a single request per URL, coordinate the callers above the handler.

Private cache only

The cache belongs to one HttpClient and does not separate users: it stores the responses to requests with an Authorization header, and ignores the directives of shared caches (s-maxage, proxy-revalidate). Do not use it as a cache shared between users, such as a proxy. See Overview.

No partial content

Requests with a Range header are sent to the server, and 206 Partial Content responses are never stored. A stored full response is not used to answer a range request.

No eviction

The stores have no size limit and no eviction policy: an entry stays until a request replaces or invalidates it, or until PruneObsoleteEntriesAsync removes it once it is obsolete. A cache that receives many distinct URLs keeps growing; prune it from time to time, and bound the size of each response with MaximumResponseSize. See Cache stores and Options.

Only GET and HEAD

Only the responses to GET and HEAD requests are stored. The responses to POST requests are never stored, even when they have explicit freshness information.