How to handle elements ID when using jQuery and ASP.NET user controls

Question

I have some user controls in ASP.NET that I am using as simply HTML, that is, without any code-behind.

I one control I have an element with a fixed ID and I am pointing it with some jQuery client scripts. For example:

<div id="slider-section"></div>

<script type="text/javascript" language="javascript">
    $(document).ready(function () {
        var slider = $('#slider-section');
        // ... do something with the jQuery Object
    });
</script>

This works very good without any problem. But there is a side effect with this. In fact, if I add two instances of the same user control on my page I will have two elements with the same ID.

Which is in your opinion a good way to handle a situation like this?

thanks

score 5 · Answer 1 · edited Nov 09 '12 at 15:07

Asp.net controllers when rendered in client side, creates a different ID, example:

you define a textbox:

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

if you check the source code of the page, you will note that textbox ID will be something like this:

id="{GUID}_Textbox1"

so what you need to do is use a selector to find the end of the ID like this:

<div id="slider-section"></div>

    <script type="text/javascript" language="javascript">
        $(document).ready(function () {      
            var slider = $('input[id$='TextBox1']').{youroptions};
            // ... do something with the jQuery Object
        });
    </script>

check documentation here : http://api.jquery.com/category/selectors/

enjoy ;)

score 2 · Accepted Answer · answered Jul 26 '11 at 13:03

2

If you added runat="server" to your simple HTML controls then they would have a page-unique ClientID like all other server controls. No codebehind code is needed.

E.g.

<div id="slider-section" runat="server"></div>

<script type="text/javascript" language="javascript">
    $(document).ready(function () {
        var slider = $('#<%=slider-section.ClientID %>');
        // ... do something with the jQuery Object
    });
</script>

answered Jul 26 '11 at 13:03

Brian Beckett

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This is definitely the way to do it. runat="server" will generate a unique id (available through ClientID) no matter how many instances of a usercontrol are in the page and no matter where they are in the page. – Brian Beckett Jul 26 '11 at 13:41
I have added the `runat="server"` attribute to my markup as you have suggested. I have also consequently updated the jquery code accordingly. But unfortunately it does not work anymore... the object is correctly found in the markup but the jquery plugin that I was using does not anymore work on that element... – Lorenzo Jul 26 '11 at 15:18
Check that the id of the element matches up to the id that you're trying to select. Check that your `slider` variable is actually populated after you try to get the element. All `runat="server"` effectively does is generate a unique id and store the element in Viewstate - it won't change it's client-side behaviour. – Brian Beckett Jul 26 '11 at 16:53
Right! it was caused by the js function that were in the control. Thanks for helping. – Lorenzo Jul 26 '11 at 21:56
What about the object name itself (var slider) - is that an issue with multiple instances of the user control? – jose Aug 10 '11 at 11:27
`var slider` is local to the function. No problem there. With n usercontrols there'll just be n anonymous functions attached to document.ready. – Brian Beckett Aug 11 '11 at 09:30

score 2 · Answer 3 · answered Jul 26 '11 at 13:07

2

Whilst browsers may not complain about multiple identical IDs, it is not correct to have them on an HTML page.

Your real problem is that you need to change the ASP.NET code that adds the User control to ensure all IDs are unique. Then your jQuery problem will also go away!

answered Jul 26 '11 at 13:07

Widor

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Thanks for your answer. The problem is that I am wrapping the user control inside a web part in a sharepoint environment. So I dont have control on when the user will add or not another instance of the control to the page. The code you are suggesting shall then be inside the control itself and this make me a little bit confusing :) – Lorenzo Jul 26 '11 at 13:13
I'd take a look at the MSDN docs on building custom controls. If the control itself doesn't assign a unique ID, the code that adds it certainly should. I think you may need to add a bit more code to your control - perhaps overriding a constructor somewhere. – Widor Jul 26 '11 at 13:17

Peter Mourfield · Answer 4 · 2011-07-26T13:09:26.547

1

I'm not sure that I completely understand your question, but based on what I think you're asking; Would changing the jQuery selector to use the html element's class solve your problem? Maybe something like this would work for you:

<div id="slider-section1" class="slider-section"></div>
<div id="slider-section2" class="slider-section"></div>

<script type="text/javascript" language="javascript">
    $(document).ready(function () {
        var slider = $('.slider-section');
        // ... do something with the jQuery Object
    });
</script>

p.s. It's not good practice to have html elements on the page with the same id/name, even if the browser supports it.

edited Jul 26 '11 at 13:09

answered Jul 26 '11 at 13:03

Peter Mourfield

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Not completely right. While your suggestion works it does not permit me to uniquely reference every single control.... – Lorenzo Jul 26 '11 at 13:11
In my opinion, this is the correct approach in this particular case. "Slider section" denotes a generic category of elements, i.e. is part of a _class_ of elements. ID is best used to identify a _specific_ element which is in some way unique. (That said, I realise it doesn't answer @Lorenzo's more general question about generating unique IDs for client controls.) – Jordan Gray Jul 26 '11 at 13:25

score 0 · Answer 5 · edited Nov 30 '11 at 00:07

0

Read the clientID of the control in your markup and put it inside a JavaScript variable or directly into your jQuery function.

ie:

<div id="slider-section"></div>

<script type="text/javascript" language="javascript">
    $(document).ready(function () {
        var slider = $('#<%= yourControl.ClientID %>');
        // ... do something with the jQuery Object
    });
</script>

edited Nov 30 '11 at 00:07

Jonathan Leffler

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answered Jul 26 '11 at 12:59

Fender

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The question is about controls that don't run on the server - i.e. no clientid. – Brian Beckett Jul 26 '11 at 13:02
oh sorry ... I thought you talk of server controls – Fender Jul 26 '11 at 13:58

score 0 · Answer 6 · answered Jul 26 '11 at 13:07

0

The whole point of an ID is to uniquely identify elements. If you want to "group" elements together you should give them the same class.

This is a pretty good explanation. http://css-tricks.com/818-the-difference-between-id-and-class/

answered Jul 26 '11 at 13:07

Jack

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thanks for your answer. Anyway I dont want to loose the chance to reference every single control uniquely... – Lorenzo Jul 26 '11 at 13:14
Then you'll have to modify your code to index the Ids of the controls created. Also, if your sliders are nested within different parent divs with unique IDs you can give them classes like people have suggested and select them uniquely based on their parents. `$('parentId').find('.slider-section');` for example. – Jack Jul 26 '11 at 13:23

How to handle elements ID when using jQuery and ASP.NET user controls

6 Answers6