Question

I have a CDN with files, and I want to create a small tool that checks for the file existence there, based on a pre-defined files list.

I tried to use WebRequest, but it seems like it to download the file. I just want to get the content length without downloading it. (similar to curl -I )

Thanks

Answer 1

You might be able to make a HEAD request to get that information.

Quote from w3.org:

The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metainformation contained
in the HTTP headers in response to a HEAD request SHOULD be identical
to the information sent in response to a GET request. This method can
be used for obtaining metainformation about the entity implied by the
request without transferring the entity-body itself. This method is
often used for testing hypertext links for validity, accessibility,
and recent modification.

The response to a HEAD request MAY be cacheable in the sense that the
information contained in the response MAY be used to update a
previously cached entity from that resource. If the new field values
indicate that the cached entity differs from the current entity (as
would be indicated by a change in Content-Length, Content-MD5, ETag or
Last-Modified), then the cache MUST treat the cache entry as stale.

From what I’ve read elsewhere, the content-length should be present in a HEAD response. But “should” doesn’t necessarily mean it always is (see: Content-Length header with HEAD requests?)