RegisterMimeFilter usage?

[BobM]

Hi, I cannot see a "managed" newsgroup or forum for IWebBrowser, so I am
posting here to get a MS rep answer if possible as I have had no luck from
the general un-managed forums...

I am using IWebBrowser2 to implement a web browser in my application.

When calling IInternetSession::RegisterMimeFilter to register a temporary
pluggable MIME filter, like...

pInternetSession->RegisterMimeFilter(pMyMimeFilterFactory, CLSID_NONE,
L"text/xml");

It appears that the pwzType parameter (L"text/xml" above) needs to have the
exact Content-Type specified, including the encoding.

For example, the above call using L"text/xml" will not register the filter
for L"text/xml; encoding=utf-8".

And for that matter, using L"text/xml; encoding=utf-8" will not work if the
http response has the

Content-Type: "text/xml;encoding=utf-8" (that is without the space between
; and encoding;

So, do I really have to make a call to RegisterMimeFilter with EVERY
possible Content-Type encoding string?

Thanks
Bob