Enabling ETag Response Caching

ETag (entity tag) is a mechanism in the HTTP protocol used to identify the version of a resource. The server returns the resource's ETag value in the response headers (for example, "abc123"), and the client can carry this value via the If-None-Match header in subsequent requests. If the resource has not changed, the server returns 304 Not Modified and does not need to retransmit the content; otherwise, it returns the new content and a new ETag.

After ETag caching is enabled, the framework handles this process automatically: the first request caches the response and the ETag, subsequent requests automatically attach If-None-Match; when a 304 status code is received, the cached content is reused directly, reducing data transmission and improving request efficiency. In weak network environments or mobile data-billing scenarios, this mechanism can significantly reduce bandwidth consumption while speeding up response times.

HttpRequestBuilder.Get("https://furion.net/")    .UseETag();HttpRequestBuilder.Get("https://furion.net/")    .UseETag(false); // Disable this feature (default value)

Notes on ETag Response Caching

Only applies to GET and HEAD requests.
If the request explicitly calls DisableCache(), the ETag feature is automatically skipped.
The cache is stored in memory by default, and can be replaced with a distributed cache (such as Redis) by implementing the IHttpETagCache interface.
The default in-memory cache does not limit the number of cache entries or the size of a single response; a large number of unique URLs or large responses may cause memory to grow continuously. To avoid this, it is recommended to implement the IHttpETagCache interface and replace the default implementation, for example:
cs
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1
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services.Replace(ServiceDescriptor.Singleton<IHttpETagCache, CustomETagCache>());
If the global request analysis tool (AddProfilerDelegatingHandler) is also enabled and you find that the response content is not printed, explicitly calling the Profiler() method on the request will resolve it.