Check if asp.net control exists with jQuery

Question

When referring asp.net control inside a MasterPage in this way:

    $(function() { 
        $('#<%=txtMunicipio.ClientID%>').autocomplete({
            source: function(request, response) {
                $.ajax({
                    url: 'http://localhost/Autocomplete/WSAutocomplete.asmx/Poblacion',
                    data: 't=' + request.term,
                    type: 'POST',
                    //contentType: 'text/xml;charset=utf-8',
                    dataType: 'xml',
                    success: function(data) {
                        response(a = $.map(splitResponse(data), function(a, n) {
                            return formatCity(a, n);
                        }));
                    }
                });
            },
            ........

I am getting error "Object expected" because control does not exist in page. How can I check if control exists before associate autocomplete function?

Thanks in advance

Is the control defined in the master page or other pages? If the latter then I don't think this will work, the control MUST be in the master. — Mantorok
– Mantorok, Commented Jun 24, 2011 at 12:31
The control is defined on other pages, not in master page, but it should work as in other pages it is working. The problem is that this page is using a Wizard, so the control is not present in all steps. — Alfonso
– Alfonso, Commented Jun 24, 2011 at 12:52

Ritik Khatwani · Accepted Answer · 2011-06-25 21:09:36Z

1

First basic thing, make sure jquery and autocomplete js files are included.

If you have a master page the ID might get changed and even if you don´t, the safest way i find is if($(´[id$=txtMunicipio]´)!=undefined && $(´[id$=txtMunicipio]´).length > 1) { //do your thing } else { //handle the problem }

and your problem might just be that you need to wrap your code around a: $(document).ready(function(){ //your code goes here });

and in case of an update panel, if you wanna run a script on every load go for: function pageLoad(){ //your code here }

answered Jun 25, 2011 at 21:09

Ritik Khatwani

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1 Comment

Alfonso Over a year ago

Ok, I was including jquery files incorrectly. So when included correctly I can use (as said by sapan): if($('#<%=txtMunicipio.ClientID%>') > 0){...

Sap · Accepted Answer · 2011-06-24 12:32:03Z

1

$("#mydiv").length > 0

http://aaronrussell.co.uk/legacy/check-if-an-element-exists-using-jquery/

answered Jun 24, 2011 at 12:32

Sap

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3 Comments

Alfonso Over a year ago

I am new to jQuery. Shoul I do: '$function(){ if($('#<%=txtMunicipio.ClientID%>').length) { $('#<%=txtMunicipio.ClientID%>').autocomplete({.... I am not sure where to put the check expression.

Sap Over a year ago

Alfonso, You should check your .NET code first it is very unlikely that the control is not getting created because $(function() { }); only runs after all the elements are added to the DOM. Also it is not $function()... it is $(function() { // Handler for .ready() called. }); How are you creating this element in .NET? Also have a look at api.jquery.com/ready

Alfonso Over a year ago

Thanks sapan, the problem was I was not referencing jQuery libraries fine from my masterpage. Now the problem is solved.

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