The HeaderValue property is used in conjunction with the
HeaderField property to set or get the values of specific
fields in the HTTP request and response headers. When the property is
set to a value, then the specified request header field is set to
this value. When the property is read, then the value associated with
the specified response header field is returned.
Note that the control automatically generates a default request
header, and it is not required that the client use the
HeaderField and HeaderValue properties unless it has a
specific need to do so.