how to load values of dropdown list control using jquery in asp.net website

Let's presume you are getting the info from the drop down list from a db ... just to make it interesting.

FIRST - the JQUERY.  Get the data from (in this case) a generic handler.  We make an AJAX GET request (passing dummy data to the handler ... since I can't predict your data architecture).  When the info has been passed successfully, we have a callback function that hanldes the population of the dropdown.

        // asp dropdownlist
        $.getJSON(
            '/generichandlers/jq_GetFromDB.ashx',
            {firstname:'Mista', lastname:'Bigg', age:43},
                function(data) {
                //callback
                populateOffices(data);
                }
        );

I'm setting this up with a hander because it will be useful for those using databases who want to call server-side functionality without the burden of viewstate or ineffective .net postbacks.  Here's the JSON string/array that is being returned from the Generic Handler but if you don't like this just make any old array and it'll do.

context.Response.Write("{'44352' : 'East Desolation', '98872' : 'DownTown Branch', '56821' : 'South Side'}");

Here's the function that populates the asp:dropdownlist: VERY IMPORTANT you have to use the name of the control that is generated from the CLR (ctl00_ContentPlaceHolder1_drpOffices)  NOT drpOffices.

function populateOffices(genArray) {
    $.each(genArray, function(val, text) {
        $('#ctl00_ContentPlaceHolder1_drpOffices').append(
            $('<option></option').val(val).html(text)
        );
    });
}

And here's the dropdownlist:

<asp:DropDownList ID="drpOffices" runat="server" />

I am presuming you are familiar with how to set this stuff up.  
       

I forgot to mention, if you bypass the .net postback and use JQuery AJAX then you need to put EnableEventValidation="false" in the page directive.