Can I use commas in a URL?

Question

I typically use URL rewriting to pass content IDs to my website, so this

 Foo.1.aspx

rewrites to

 Foo.aspx?id=1

For a specific application I need to pass in multiple IDs to a single page, so I've rewritten things to accept this:

 Foo.1,2,3,4,5.aspx

This works fine in Cassini (the built-in ad hoc web server for Visual Studio) but gives me "Internet Explorer cannot display the webpage" when I try it on a live server running IIS. Is this an IIS limitation? Should I just use dashes or underscores instead of commas?

Answer 1

See if this works:

Foo.1,2,3,4,5.aspx

(, is the comma entity).

Answer 2

The right way to accept multiple ids is like this:

Foo.aspx?id=1;id=2;id=3;id=4;id=5

Note that's just what the target is. When re-writing urls, you can set your own rules to a certain extent for what you want the source to look like.

I had to learn this on StackOverflow, too. See this question:
http://stackoverflow.com/questions/63463/split-out-ints-from-string

Answer 3

The comma is allowed in the path, query string and fragment according to spec. It wouldn't surprise me if IE doesn't conform to the spec though. Try the entity as Claudiu suggests, but I don't know why that would be necessary.

Answer 4

Commas are allowed in the filename part of a URL, but are reserved characters in the domain*, as far as I know.

What version of IE are you using? I've come across the odd report of IE5.5 truncating URLs on a comma (link here, but have tested URLs with commas in IE7 and it seems to be OK, so if there was an IE bug, it doesn't seem to be there any more - could it be an IIS issue?

I'm wondering if the page error is due to a rule failure with the mod_rewrite - can you post the rule which is matching multiple ids and passing them off to your Foo.aspx? Is there any chance that it's only matching Foo.N,N, and failing on more commas?

---

* From the URI RFC:

2.2. Reserved Characters

Many URI include components consisting of or delimited by, certain special characters. These characters are called "reserved", since their usage within the URI component is limited to their reserved purpose. If the data for a URI component would conflict with the reserved purpose, then the conflicting data must be escaped before forming the URI.

 reserved    = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
                "$" | ","

The "reserved" syntax class above refers to those characters that are allowed within a URI, but which may not be allowed within a particular component of the generic URI syntax

Answer 5

Answer

The problem was the commas. I'm guessing that IIS was having an issue with it (not IE) since IE was able to display it fine on localhost.

At any rate I just changed the URL format to this and it works fine:

Foo.1-2-3-4-5.aspx

Answer 6

If you'd put in place a front controller then you could do something like;

index.aspx?c=Foo/1/2/3/4

The Front Controller would pick up the method name and the parameters to pass to it. This is a pretty common technique nowadays.

Answer 7

I recall that Url Routing by default first checks to see if the file exists, and commas are not legal in filenames, which is parhaps why you are getting errors. IIS may have legacy code that aborts the request before it can get to asp.net for processing.

Scott Hanselman's blog post talks a bit about this and may be relevant for you.

---

As general comment: Url rewriting is typically used to make a url friendly and easy to remember.

~/page.aspx?id=1,2,3,4 is neither worse nor better than ~/page/1-2-3-4.aspx : both are difficult to use so why go through the extra effort? Avoid creating new url forms just because you can. Users, help desk, and other developers will just be confused.

Url rewriting is best utilized to transform

~/products/view.aspx?id=1
~/products/category.aspx?type=beverage

into

~/products/view/1
~/products/category/beverage

Answer 8

Try using %2c in the URL to replace the commas.