$(function(){
            $("#btnAdd").click(function(){
                //using JQuery ajax to call the handler method and get the select list options.
               $.ajax({
                    type: "Get",
                    url: "/Index?handler=GetTypeList",  
                    success: function (data) {
                        //add new select element:
                        var newselect = "<select>"
                        $.each(data, function (i, item) {
                            newselect += `<option value="${item.value}">${item.text}</option>`;
                        });
                        newselect += "</select>";
                        //generate the new form group
                        var newitem = "<div class='form-group firstgroup'><label class='control-label' for='Bill_Type'>Type</label> "+ newselect +" <input type='button' value='Add' id='btnAdd'> </div>";
                        //append the new elements to the main form.
                        $("#mainform").append(newitem);
                    },
                    error: function (response) {
                        alert(response.responseText);
                    }
                });
            });
        });