How to bind controls values based on the combo box change event?

You can have a page method which will get the values from database and return in JSON formatted string. You can also use asmx web methods to return the same result.

$('#ddlName').change(function () {
   PopulatePersonDetail($('#ddlName').val());
});

Call the method using jQuery 'ajax' method and get the JSON object which contains the actual values.

function PopulatePersonDetail(){
var name = 'smruti';
$.ajax({
        type: "POST",
        url: "../WebMethods/WebService.asmx/GetPersonDetailsByName",
        data: "{key:'" + name + "'}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        async: false,
        success: function (response) {
            $.each(JSON.parse(response.d), function (key, value) {
                 var result = $.parseJSON(response.d);//result contains all detail
                 $('#txtAge').val(result.Age); // like this all other fields also can be populated.
            });
        },
        error: function (XMLHttpRequest, textStatus, errorThrown) {
            ShowError(failMessage, 450, 100);
        }
    });
}

Here is the web method which is called to get data.

[WebMethod(EnableSession = true)]
        public string GetPersonDetailsByName(string name)
        {
            string jsonData = string.Empty;
            Person personData = new Person();
            List<Person> PersonEntityList = personData.GetPersonDetailsByName(string name);
            jsonData = Parser.EntityToJSon(PersonEntityList);
            return jsonData;
        }

Hope this will definitely be helpful.