Question

Is Request.Headers["Header-Name"] in ASP.NET case-sensitive? And if it is, how should I get a certain header (e.g. “X-requested-with”) if I don’t know for sure what case the client will send it in?

Answer 1

no they are case-insensitive as per RFC2616

4.2 Message Headers

HTTP header fields, which include general-header (section 4.5),
request-header (section 5.3), response-header (section 6.2), and
entity-header (section 7.1) fields, follow the same generic format as
that given in Section 3.1 of RFC 822 [9]. Each header field consists
of a name followed by a colon (“:”) and the field value. Field names
are case-insensitive. The field value MAY be preceded by any amount
of LWS, though a single SP is preferred. Header fields can be
extended over multiple lines by preceding each extra line with at
least one SP or HT. Applications ought to follow “common form”, where
one is known or indicated, when generating HTTP constructs, since
there might exist some implementations that fail to accept anything