Question

I’ve got a dropdown list that is being populated via a webservice using ASP>NET AJAX. On the success callback of the method in javascript, I’m populating the dropdown via a loop:

function populateDropDown(dropdownId, list, enable, showCount) {     var dropdown = $get(dropdownId);     dropdown.options.length = 1;         for (var i = 0; i < list.length; i++) {         var opt = document.createElement('option');         if (showCount) {             opt.text = list[i].Name + ' (' + list[i].ChildCount + ')';         } else {             opt.text = list[i].Name;         }         opt.value = list[i].Name;         dropdown.options.add(opt);     }     dropdown.disabled = !enable;     } 

However when I submit the form that this control is on, the control’s list is always empty on postback. How do I get the populated lists data to persist over postback?

Edit: Maybe I’m coming at this backwards. A better question would probably be, how do I populate a dropdown list from a webservice without having to use an updatepanel due to the full page lifecycle it has to run through?

Answer 1

Although I’m not really sure how it does it the CascadingDropDown in the AJAX Control Toolkit does support this.

This is the line that appears to do it:

AjaxControlToolkit.CascadingDropDownBehavior.callBaseMethod(this, 'set_ClientState', [ this._selectedValue+':::'+text ]); 

But the simplest idea would be to put the selected value into a hidden input field for the postback event.