public static CacheValidationStatus OnValidateRequest(HttpRequestCacheValidator ctx) {
/*
Some HTTP methods MUST cause a cache to invalidate an entity. This is
either the entity referred to by the Request-URI, or by the Location
or Content-Location headers (if present). These methods are:
PUT, DELETE, POST.
A cache that passes through requests for methods it does not
understand SHOULD invalidate any entities referred to by the
Request-URI
*/
if (ctx.RequestMethod >= HttpMethod.Post && ctx.RequestMethod <= HttpMethod.Delete)
{
if (ctx.Policy.Level == HttpRequestCacheLevel.CacheOnly)
{
// Throw because the request must hit the wire and it's cache-only policy
ctx.FailRequest(WebExceptionStatus.RequestProhibitedByCachePolicy);
}
// here we could return a hint on removing existing entry, but UpdateCache should handle this case correctly
return CacheValidationStatus.DoNotTakeFromCache;
}
//
// Additionally to said above we can only cache GET or HEAD, for any other methods we request bypassing cache.
//
if (ctx.RequestMethod < HttpMethod.Head || ctx.RequestMethod > HttpMethod.Get )
{
if (ctx.Policy.Level == HttpRequestCacheLevel.CacheOnly)
{
// Throw because the request must hit the wire and it's cache-only policy
ctx.FailRequest(WebExceptionStatus.RequestProhibitedByCachePolicy);
}
return CacheValidationStatus.DoNotUseCache;
}
if (ctx.Request.Headers[HttpKnownHeaderNames.IfModifiedSince] != null ||
ctx.Request.Headers[HttpKnownHeaderNames.IfNoneMatch] != null ||
ctx.Request.Headers[HttpKnownHeaderNames.IfRange] != null ||
ctx.Request.Headers[HttpKnownHeaderNames.IfMatch] != null ||
ctx.Request.Headers[HttpKnownHeaderNames.IfUnmodifiedSince] != null )
{
// The _user_ request contains conditonal cache directives
// Those will conflict with the caching engine => do not lookup a cached item.
if(Logging.On)Logging.PrintWarning(Logging.RequestCache, SR.GetString(SR.net_log_cache_request_contains_conditional_header));
if (ctx.Policy.Level == HttpRequestCacheLevel.CacheOnly)
{
// Throw because the request must hit the wire and it's cache-only policy
ctx.FailRequest(WebExceptionStatus.RequestProhibitedByCachePolicy);
}
return CacheValidationStatus.DoNotTakeFromCache;
}
return CacheValidationStatus.Continue;
}
//
