ASP.NET - Ajax requests with jQuery

I have this textBox that triggers 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 box 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 perfectly. The only problem I am having is that when I update my formView code to save this entry, I cannot see the values ​​that were set for this dropdown. Since I am populating this client side dropdown menu, my guess is that ASP.NET does not handle this.

Does anyone have any ideas?

Apparently when I enable / disable the EnableEventValidation property for this page, I sometimes get the correct value .....

Thank!