Value of dropdownlist in asp.net disappears after changing the value of dropdownlist by javascript

Question

In my application, I have created an ajax autocompelete extender text box.Once the user chooses the value, I want to insert that value in my dropdownlist. The code for that purpose is:

function GetCode(source, eventArgs) {
         var hfield = $get('<%=this.HiddenID.ClientID%>');
         hfield.value = eventArgs.get_value();

       //hfield has the value selected in the autocomplete text box

        var abc = document.getElementById('<% =DropDownList2.ClientID %>');

         for (var i = 0; i < abc.length ; i++) {
             alert(abc.options[i].value);
             if (abc.options[i].value == hfield.value) {
                 abc.options[i].selected = true;
                 break;
             }
         }
     }

The problem here is: My value is not showing in the dropdownlist. When I tried to debug the code, I realized that the value does come in the dropdownlist but when this code exits, the value disappears from the dropdownlist.

I have no idea why the values are disappearing! Please help! Thank you!

Icarus · Accepted Answer · 2013-06-19 13:54:03Z

3

It's dissapearing because you are binding the data on the server-side initially and when you make the ajax request to insert the new record into the dropdownlist, the ViewState for the DropDownList had no knowledge of this new value and therefore renders what it had before.

answered Jun 19, 2013 at 13:54

Icarus

64k14 gold badges102 silver badges116 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Ankita Over a year ago

ok now I get it! But then what should I do to make my values not disappear?

Icarus Over a year ago

The way to do it is how @speti43 suggested: add a Hidden element and set its value to whatever the selected value is in the dropdown. After postback, restore this value yourself to the dropdown. You basically have to manage the state manually, unfortunately :-/

speti43 · Accepted Answer · 2013-06-19 14:02:38Z

0

If you want to modify a server side dropdownlist's element collection on client-side by javascript, you can get eventvalidation error on next postback. It would be dangerous if this behaviour wouldn't be because you could modify these controls collection by xss attack, and submit your extra added value to the server.

answered Jun 19, 2013 at 14:02

speti43

3,0622 gold badges22 silver badges26 bronze badges

2 Comments

Ankita Over a year ago

I am not adding any extra value to my dropdown list.I am just trying to change the selection inside the dropdownlist by javascript. Is there some other way to do this?

speti43 Over a year ago

Yeah, do it on server side. You have the value on server side, so you can make there the selection. Or on every page_load check your hiddenfield's value, and set there the selected value of dropdown. But this would be like you want to manage "viewstate" by manually.

Collectives™ on Stack Overflow

Value of dropdownlist in asp.net disappears after changing the value of dropdownlist by javascript

2 Answers 2

2 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related