Trouble encoding a u umlaut with in a .Net http handler

Question

I have a JavaScript request going to a ASP.Net (2.0) HTTP handler which passes the request to a java web service. In this system special characters, such as those with an accent do not get passed on correctly.

E.G.

• Human input: Düsseldorf
• becomes a JavaScript asynch request to http://site/serviceproxy.ashx?q=D%FCsseldorf, which is valid in ISO-8859-1 as well as in UTF-8 as far as I can tell. (unless it's %c3%bc in UTF-8)
• HttpContext.Current.Request.QueryString.Get("q") returns D�sseldorf which is where trouble begins.
• but HttpUtility.UrlEncode(HttpContext.Current.Request.QueryString.Get("q"), Encoding.GetEncoding("ISO-8859-1")) returns D%3fsseldorf (a '?')
• and HttpUtility.UrlEncode(HttpContext.Current.Request.QueryString.Get("q"), Encoding.UTF8) returns D%ef%bfsseldorf

So it the value doesn't get decoded nor re-encoded correctly to be passed on to the java service.

• Notice HttpContext.Current.Request.Url.Query is ?q=D%FCsseldorf&output=json&from=1&to=10
• while HttpContext.Current.Request.QueryString.ToString() is q=D%ufffdsseldorf&output=json&from=1&to=10

Why is this, and how can I tell the HttpContext to honor the request headers which include:

Content-Type=application/x-www-form-urlencoded;+charset=UTF-8

and decode the URL's QueryString using the UTF-8 charset.

Addendum: As the answer notes, the trouble lies not so much in the decoding as the encoding; using escape() in JavaScript does not escape according to UTF-8, while using encodeURIComponent() does.

Answer 1

I don't know what the default character encoding used by your server (IIS?) is, or if it can be changed, but I can tell you a few things that might help.

0xFC is the ISO-8859-1 encoding for ü. While the Unicode code point is U+00FC, when encoded with UTF-8, this requires two bytes, and becomes 0xC3 0xBC.

If a UTF-8 decoder were to see the illegal byte sequence 0xFC, it would decode it as a Unicode "replacement character", U+FFFD, and pick up where it saw the beginning of another valid byte sequence, in this case 's'.

The reason you get %3f is that '?' is the "replacement character" for the Latin character set, similar to � in the Unicode character set.

I believe what you're seeing is the client encoding with ISO-8859-1, but the server is decoding with UTF-8. As soon as it hits the server, your data is corrupted. I recommend that you modify the client to use UTF-8 encoding; it should be requesting http://site/serviceproxy.ashx?q=D%C3%BCsseldorf

It sounds like you are constructing these URLs from JavaScript, so you should use the encodeURI and encodeURIComponent functions, not escape.