Hi,

if you don't want to have a postback after every selection, then you shouldn't set AutoPostBackFlag to On or Async. It is not possible to cancel selection and have selection at once at the same time, once the list is closed.

I suggest the following approach - keep your current code, but only remove the autopostback flags settings, so that there is no postback.

In the DropDownClosed client-side event handler, do that:

    function dropDownClosed(sender, args) {

            var dd = sender._callbackManager.createCallbackObject();

            sender._callbackManager.execute(dd, true);

        }

It's always good to also put a flag, so that in the closing handler, it knows when to do postback. I.e. do postback only when there was change in the selection. Otherwise it will do an async postback everytime the dropdown is closed. 

If this doesn't help and the dropdown is still open, i would handle the Initialize client-side event, check whether the dropdown is open and if it is , close it, or just always close it by calling this function:

dropDown.closeDropDown();

Then the functions that you already have become like this:

    <script type="text/javascript">

      var selectionChanged = false;

        function selectedIndexChanged(sender, eventArgs) {

               selectionChanged=true;

            /*

*/

        }

        function dropDownClosed(sender, args) {

            if (selectionChanged) 

           {

                    var dd = sender._callbackManager.createCallbackObject();

                    sender._callbackManager.execute(dd, true);

                    selectionChanged=false;

            }

        }

    </script>

This should work fine, i don't know why it leaves the dropdown still open. Could you try and let me know whether it works? 

Thanks,

Angel