Question

i´m new developing on asp.net mvc, and even newer using jquery, so this is my problem: i have a few dropdown list that are filled dinamically using the data of another dropdown or textbox, and the data of those drop down is used for another drop down, like a chain, my problem rigth now is that the dropdown sometimes just have one answer/option, and if i try to select that option jquery doesn´t activate the $(“#anything”).change() event, ’cause i have just one option, how i handle it?

http://imageshack.us/photo/my-images/20/sinttulolp.jpg/

for example this i need the data of the red circle for filling the blue circle, but the red circle just have one option and if i click nothing happens

code:

$(document).ready(function() {

            $("#tbClave1").autocomplete({
                minLength: 1,
                source: getClave1,
                select: function(event, ui) {
                    updateClave2(ui.item.value);

                }
            });

            $("#tbClave1").change(function() {
                if ($("#tbClave1").val().length == 4) {
                    updateClave2($("#tbClave1").val());
                }
            });

            $("#ddClave2").change(function() {
                updateClave3($("#tbClave1").val(), $("#ddClave2").val());
                updateNombre($("#tbClave1").val(), $("#ddClave2").val());
                if ($("#ddTipoArticulo").val() == "A" ||
                    $("#ddTipoArticulo").val() == "B" ||
                    $("#ddTipoArticulo").val() == "L") {
                    updatePrecioA($("#tbClave1").val(), $("#ddClave2").val());
                } else { 
                    if ($("#ddTipoArticulo").val() == "N" ||
                         $("#ddTipoArticulo").val() == "H"){
                         updatePrecioB($("#tbClave1").val());
                    }
                }
            });

            $("#ddClave3").change(function() {
                updateClave4($("#tbClave1").val(), $("#ddClave2").val(), $("#ddClave3").val());
            });
        });

Edit: example of how i fill one of the dropdownlist

Jquery

function updateClave2(cod) {

            var dd = document.getElementById("ddClave2");
            dd.options.length = 0;
            dd.options[0] = new Option("Espere...");
            dd.selectedIndex = 0;
            dd.disabled = true;
            codigo = cod;
            tipoArt = $("#ddTipoArticulo").val();
            // Control de errores
            $("#ddClave2").ajaxError(function(event, request, settings) {
                dd.options[0] = new Option("No se Cargaron Datos");
            });
            // Obtenemos los datos...
            $.ajax({
                url: '/Home/GetClave2',
                dataType: 'json',
                data: { words: codigo, tipoArticulo: tipoArt },
                success: function(data, textStatus, jqXHR) {
                    $.each(data, function(i, item) {
                        dd.options[i] = new Option(item["clave2"], item["clave2"]);
                    });
                    dd.disabled = false;
                }
            });
        }

Controller

public ActionResult GetClave2(string words, string tipoArticulo){
List mySource = miConexion.Clave2(username, password, words, tipoArticulo);
return Json(mySource);
}

Answer 1

As Alex Mendez has wrote, adding a default item to each dropdownlist with text like “Select One” seems to be your easiest answer. You’ll also need to do some handling in case the user re-selects the default “Select One option.” To add default values to your .Net dropdowns try out this code:

YourListID.Items.Insert(0, new ListItem("Select One", "Select One");

or:

<asp:DropDownList ID="YourListID" runat="server" AppendDataBoundItems="true">
    <asp:ListItem Text="Select One" Value="Select One" Selected="true" />
</asp:DropDownList>

EDIT (Missed the MVC)
and in MVC when you bind your initial ViewData just make sure to have your “Select One” in the liest:

Dictionary<int, string> dictionaryList = DropDownListItems();
ViewData["ModelData"] = new SelectList(dictionaryList, "Key", "Value")