Standard token for encoding parentheses for HTML Ids?

Question

I have to encode strings to remove parentheses for Ids for HTML elements.

Parentheses (these ones (,)) aren't valid in HTML Ids, are there standard strings (like those used in URLs) to use?

Is there an existing method that can be used in ASP.NET MVC?

N.B. System.Web.Mvc.HttpUtility.HtmlEncode(string), does not encode parentheses.

In what situation are parentheses naturally appearing in your Ids? — Kirk Woll, Jun 15 '11 at 14:26
If you look at the Body of a Linq expression that includes a collection using the `collectionName[index]` method to access it, the function returns `collectionName.get_Item(index)`. — StuperUser, Jun 15 '11 at 14:36
And potentially dangerous -- the Id attribute would be easily hackable. — Kirk Woll, Jun 15 '11 at 14:48
+1 You're right. I am too busy thinking about an answer to the question and not asking whether or not it should be done! — Tom Chantler, Jun 15 '11 at 14:53
@Kirk Woll - easy to modify.. it depends *how* the value is used, consumed or decoded to determine how hackable it is. — Andrew, Jun 15 '11 at 15:25

score 3 · Accepted Answer · edited May 23 '17 at 11:50

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As per the HTML specification (and this question about id's) parentheses aren't allowed in the HTML id attribute. If you need them, you could use string replace, e.g.:

//  ( = 'op--'  Opening Parenthesis
//  ) = 'cp--'  Closing Parenthesis

string id = "collectionName.get_Item(index)";

// encode
string encodedId = id.Replace("(", "op--").Replace(")", "cp--");

// decode
string decodedId = encodedId.Replace("op--", "(").Replace("cp--", ")");

edited May 23 '17 at 11:50

Community

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answered Jun 15 '11 at 14:29

Andrew

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This sounds like the best approach, especially being able to have `UrlDecode()` to decode. – StuperUser Jun 15 '11 at 14:44
Cool. Well now we have two answers which are essentially the same and I reckon they're probably both right. – Tom Chantler Jun 15 '11 at 15:05
Are there any standard tokens to use? – StuperUser Jun 15 '11 at 15:12
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@StuperUser - no, there aren't any standard tokens for representing parentheses in HTML `id` elements - if you need them, you'll have to encode / decode them yourself :o/ – Andrew Jun 15 '11 at 15:23
@Dommer - :o) I think you understood it first ;o) – Andrew Jun 15 '11 at 15:28

Tom Chantler · Answer 2 · 2011-06-15T14:50:47.340

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I don't think I understand the question, cos it feels like the answer is to substitute [ and ]. Or even %28 and %29 from the Wikipedia link you gave.

Have I got hold of the wrong end of the stick?

EDIT: From what has been said in the comments, it seems that %28 and %29 are not okay as the % character is also invalid, in which case you could select a substitute that won't appear elsewhere.

EG Something like ( becomes ---28--- (or even ---openbracket---) or something else you can guarantee won't appear elsewhere in the ID (which should be possible).

edited Jun 15 '11 at 14:50

answered Jun 15 '11 at 14:27

Tom Chantler

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You've got it right Dommer, I was wondering whether there was anything more standard for Html Id s than the URL codes. – StuperUser Jun 15 '11 at 14:41
I don't understand how it helps to encode them: neither paranethes ('(' and ')') **nor** the percent character '%' are [valid characters in an HTML Id attribute](http://stackoverflow.com/questions/70579/what-are-valid-values-for-the-id-attribute-in-html). – Kirk Woll Jun 15 '11 at 14:43
In that case it looks like some kind of substitution is required, which is always a bit risky. Something like `(` becomes `---28---` (or even `---openbracket---`) or something else you can guarantee won't appear elsewhere in the ID. – Tom Chantler Jun 15 '11 at 14:47
Are there any standard tokens to use? – StuperUser Jun 15 '11 at 15:11
In C# `"get_Item(28)"` and `"get_Item(29)"` WILL encode to `"get_Item---28---28---29---"` and `"get_Item---28---29---29--"`. To prevent any issues decoding, `.Replace("---28---","(")` must be called BEFORE `.Replace("---29---","(")`. They will however still decode without any collisions caused by the end of the "(" token and start of the ")" token creating instances of "---28---" and "---29---" in the string. – StuperUser Jun 16 '11 at 14:04
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In that case it would be safer to use something like `--openbracket--` or `--ob--` and `--closebracket--` or `--cb--`. You could obviously tailor this to your own scenario - as this would cause problems with getItem(openbracket) ;-p – Tom Chantler Jun 16 '11 at 15:10

score 0 · Answer 3 · answered Jun 15 '11 at 14:31

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If the elements are dynamically created then why not just do a .Replace on the id changing parentheses for, say, underscores?

If the elements are not dynamically created then why do they have parentheses in the ids?!

answered Jun 15 '11 at 14:31

Phill

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They are dynamically created. Using `_` is undesirable since it's not standard and may be used in other parts of the id, so make decoding accurately impossible. – StuperUser Jun 15 '11 at 14:38
Does the id follow a pattern that a regex could be used to match the inner part of the id e.g. a number surrounded in parentheses? Do the brackets occur in a predictable position in the string? If not, then with any of the solutions given you will need to ensure to check that the new magic character does not exist in the id and escape it if it does. – Phill Jun 15 '11 at 22:02

Standard token for encoding parentheses for HTML Ids?

3 Answers3