The problem comes from the combination Firefox/Asp.Net. When you manually entered a URL in Firefox's address bar, if the url contains french or swedish characters, Firefox will encode the url with "ISO-8859-1" by default.
But when asp.net recieves such a url, it thinks that it's utf-8 encoded ... And encoded characters become "U+fffd". I couldn't find a way in asp.net to detect that the url is "ISO-8859-1". Request.Encoding is set to utf-8 ... :(
Several solutions exist :
put <globalization requestEncoding="iso-8859-1" responseEncoding="iso-8859-1"/>
in your Web.config. But your may comme with other problems, and your application won't be standard anymore (it will not work with languages like japanese) ... And anyway, I prefer using UTF-8 !
go to about:config in Firefox and set the value of network.standard-url.encode-query-utf8
to true. It will now work for you (Firefox will encode all your url with utf-8). But not for anybody else ...
The least worst solution I could come with was to handle this with code. If the default decoding didn't work, we reparse QueryString with iso8859-1 :
string query = Request.QueryString["search"];
if (query.Contains("%ufffd"))
query = HttpUtility.ParseQueryString(Request.Url.Query, Encoding.GetEncoding("iso-8859-1"))["search"];
query = HttpUtility.UrlDecode(query);
It works with hyperlinks and manually-entered url, in french, english, or japanese. But I don't know how it will handle other encodings like ISO8859-5 (russian) ...
Does anyone have a better solution ?
This solves only the problem of manually-entered url. In your hyperlinks, don't forget to encode url parameters with HttpUtility.UrlEncode on the server, or encodeURIComponent on the javascript code. And use HttpUtility.UrlDecode to decode it.