ASP.NET - Ajax requests with jQuery

Question

Hi,

I've got this textBox which triggers off an ajax request using jQuery:

<asp:TextBox ID="postcodeTextBox" runat="server" Text='<%# Bind("POSTAL_ZIP_CODE") %>'>

$(document).ready(PageLoad);

function PageLoad() {
    $(container + 'parentProjectTextBox').change(GetProjectName);
}

function GetProjectName() {
    var projectNumber = $(this).val();
    if (projectNumber == '') return;
    $(container + 'parentProjectPanel').block({ message: '<img src="../Resources/RadControls/Ajax/Skins/Default/loading7.gif" />' });
    $.ajax({
        type: 'POST',
        url: projectMasterWebServicesUrl + 'GetProjectName',
        data: "{'projectNumber':'" + projectNumber + "'}",
        contentType: 'application/json; charset=utf-8',
        dataType: 'json',
        success: GetProjectNameOnSuccess,
        error: GetProjectNameOnError
    });
}

This ajax request gets a list to populate this dropdown:

                        <asp:DropDownList ID="cityDropDownList" runat="server" OnDataBound="cityDropDownList_DataBound">
                            <asp:ListItem Text="...Select..." Value="0">
                            </asp:ListItem>
                        </asp:DropDownList>

Everything works fine. The only problem I'm having is that when I update my formView priod to saving that record I can't see the value that was set to that dropdown. As I'm populating this dropdown in the client side I supose ASP.NET loses track of that ....

Does anyone have any insights?

Apparently when I switch on/off the EnableEventValidation property for that page I sometimes get the correct value.....

Thanks !

Answer 1

You should create a hidden field store that value. Update that HiddenField in your Javascript and then read it on the server side. Also, if you have EventValidation=true and you change the items in the dropdown list you will get well known exceptions.

Answer 2

This may not be the problem...but are you checking for Page.IsPostBack in your Page_Load?

I've made that mistake way too many times.

If you are loading that drop down control from the Page_Load, and you are not checking if (!Page.IsPostback) you will reload the control. Then when you get the value from the drop down...the value is gone because you reloaded the dropdown.