System.Net.Cache.FtpRequestCacheValidator.UpdateCache C# (CSharp) Method

        protected internal override CacheValidationStatus UpdateCache()
        {
            if (HttpProxyMode)
                return base.UpdateCache();

            // An combined cace+wire response is not supported if user has specified a restart offset.
            CacheStreamOffset = 0L;

            if (RequestMethod == HttpMethod.Other)
            {
                if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_not_updated_based_on_policy, Request.Method));
                return CacheValidationStatus.DoNotUpdateCache;
            }

            if (ValidationStatus == CacheValidationStatus.RemoveFromCache) {
                if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_removed_existing_invalid_entry));
                return CacheValidationStatus.RemoveFromCache;
            }

            if (Policy.Level == RequestCacheLevel.CacheOnly) {
                if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_not_updated_based_on_policy, Policy.ToString()));
                return CacheValidationStatus.DoNotUpdateCache;
            }

            FtpWebResponse resp = Response as FtpWebResponse;

            if (resp == null)
            {
                if(Logging.On)Logging.PrintWarning(Logging.RequestCache, SR.GetString(SR.net_log_cache_not_updated_because_no_response));
                return CacheValidationStatus.DoNotUpdateCache;
            }

            //
            // Check on cache removal based on the request method
            //
            if (RequestMethod == HttpMethod.Delete || RequestMethod == HttpMethod.Put)
            {
                if (RequestMethod == HttpMethod.Delete ||
                    resp.StatusCode == FtpStatusCode.OpeningData ||
                    resp.StatusCode == FtpStatusCode.DataAlreadyOpen ||
                    resp.StatusCode == FtpStatusCode.FileActionOK ||
                    resp.StatusCode == FtpStatusCode.ClosingData)
                {
                    if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_removed_existing_based_on_method, Request.Method));
                    return CacheValidationStatus.RemoveFromCache;
                }
                if(Logging.On)Logging.PrintWarning(Logging.RequestCache, SR.GetString(SR.net_log_cache_existing_not_removed_because_unexpected_response_status, (int)resp.StatusCode, resp.StatusCode.ToString()));
                return CacheValidationStatus.DoNotUpdateCache;
            }

            if (Policy.Level == RequestCacheLevel.NoCacheNoStore) {
                if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_removed_existing_based_on_policy, Policy.ToString()));
                return CacheValidationStatus.RemoveFromCache;
            }

            if (ValidationStatus == CacheValidationStatus.ReturnCachedResponse)
            {
                // have a response still returning from cache means just revalidated the entry.
                return UpdateCacheEntryOnRevalidate();
            }

            if (resp.StatusCode != FtpStatusCode.OpeningData 
                && resp.StatusCode != FtpStatusCode.DataAlreadyOpen
                && resp.StatusCode != FtpStatusCode.ClosingData)
            {
                if(Logging.On)Logging.PrintInfo(Logging.RequestCache, SR.GetString(SR.net_log_cache_not_updated_based_on_ftp_response_status, FtpStatusCode.OpeningData.ToString() + "|" + FtpStatusCode.DataAlreadyOpen.ToString() + "|" + FtpStatusCode.ClosingData.ToString(), resp.StatusCode.ToString()));
                return CacheValidationStatus.DoNotUpdateCache;
            }

            // Check on no-update or cache removal if restart action has invalidated existing cache entry
            if (((FtpWebRequest)Request).ContentOffset != 0L)
            {
                if(Logging.On)Logging.PrintWarning(Logging.RequestCache, SR.GetString(SR.net_log_cache_update_not_supported_for_ftp_restart, ((FtpWebRequest)Request).ContentOffset.ToString(CultureInfo.InvariantCulture)));
                if (CacheEntry.LastModifiedUtc != DateTime.MinValue && resp.LastModified.ToUniversalTime() != CacheEntry.LastModifiedUtc)
                {
                    if(Logging.On)Logging.PrintWarning(Logging.RequestCache, SR.GetString(SR.net_log_cache_removed_entry_because_ftp_restart_response_changed, CacheEntry.LastModifiedUtc.ToString("r", CultureInfo.InvariantCulture), resp.LastModified.ToUniversalTime().ToString("r", CultureInfo.InvariantCulture)));
                    return CacheValidationStatus.RemoveFromCache;
                }
                return CacheValidationStatus.DoNotUpdateCache;
            }

            return UpdateCacheEntryOnStore();
        }