Alex Rivera | Logout

What's the difference between Request.Url.Query and Request.QueryString?

Asked 2010-02-08T04:50:11.600
13

I have been tracking down a bug on a Url Rewriting application. The bug showed up as an encoding problem on some diacritic characters in the querystring.

Basically, the problem was that a request which was basically /search.aspx?search=heřmánek was getting rewritten with a querystring of "search=he%c5%99m%c3%a1nek"

The correct value (using some different, working code) was a rewrite of the querystring as "search=he%u0159m%u00e1nek"

Note the difference between the two strings. However, if you post both you'll see that the Url Encoding reproduces the same string. It's not until you use the context.Rewrite function that the encoding breaks. The broken string returns 'heÅmánek' (using Request.QueryString["Search"] and the working string returns 'heřmánek'. This change happens after the call to the rewrite function.

I traced this down to one set of code using Request.QueryString (working) and the other using Request.Url.Query (request.Url returns a Uri instance).

While I have worked out the bug there is a hole in my understanding here, so if anyone knows the difference, I'm ready for the lesson.

c# .net url url-rewriting query-string
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What you indicated as the "broken" encoded string is actually the correct encoding according to standards. The one that you indicated as "correct" encoding is using a non-standard extension to the specifications to allow a format of %uXXXX (I believe it's supposed to indicate UTF-16 encoding).

In any case, the "broken" encoded string is ok. You can use the following code to test that:

Uri uri = new Uri("http://www.example.com/test.aspx?search=heřmánek");
Console.WriteLine(uri.Query);
Console.WriteLine(HttpUtility.UrlDecode(uri.Query));

Works fine. However... on a hunch, I tried UrlDecode with a Latin-1 codepage specified, instead of the default UTF-8:

Console.WriteLine(HttpUtility.UrlDecode(uri.Query, 
           Encoding.GetEncoding("iso-8859-1")));

... and I got the bad value you specified, 'heÅmánek'. In other words, it looks like the call to HttpContext.RewritePath() somehow changes the urlencoding/decoding to use the Latin-1 codepage, rather than UTF-8, which is the default encoding used by the UrlEncode/Decode methods.

This looks like a bug if you ask me. You can look at the RewritePath() code in reflector and see that it is definitely playing with the querystring - passing it around to all kinds of virtual path functions, and out to some unmanaged IIS code.

I wonder if somewhere along the way, the Uri at the core of the Request object gets manipulated with the wrong codepage? That would explain why Request.Querystring (which is simply the raw values from the HTTP headers) would be correct, while the Uri using the wrong encoding for the diacriticals would be incorrect.

answered 2010-02-08T06:34:05.990

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