CustomValidator with Client JavaScript

I had crafted a custom validator for an DNN web page with a function to validate form elements.

Using the DNN pop-up calendar, with appropriate date formatting according to the browser, had issues with visitors not setting the language within the browser correctly. It was also decided that using 3 dropdownlists would provide a better control of the selection, and less issue with date selection on mobile devices using the pop up calendar.

I added 3 drop down lists to a web page to facilitate date selection.

To ensure that the date was valid I created a custom control to be referenced on the page with validateDate()

Initially I found that the function was firing, but that the status wasn’t being returned.

The JavaScript function was amended, requiring both sender and args parameters, like so:

<script type="text/javascript">
function validateDate(sender,args) {
    var ddlDay = $("#<% = ddlTheDay.clientid %>");
    var ddlMonth = $("#<% = ddlTheMonth.clientid %>");
    var ddlYear = $("#<% = ddlTheYear.clientid %>");

    document.getElementById('<% = cvTheDay.clientid %>').style.display = 'none';
    document.getElementById('<% = cvTheMonth.clientid %>').style.display = 'none';
    document.getElementById('<% = cvTheYear.clientid %>').style.display = 'none';

    // check date was selected
    if (ddlDay.val() < 0 ||
        ddlMonth.val() < 0 ||
        ddlYear.val() < 0) { // if ($('.validateDate').hasClass('validDate')){ // $('.validateDate').toggleClass('inValidDate validDate'); //} args.IsValid = false; return false; } // ensure days value correct if (ddlDay.val() > daysInMonth(ddlMonth.val(), ddlYear.val())) {
        args.IsValid = false;
        return false;

    // check date is valid
    var dobDate = new Date(ddlYear.val(), ddlMonth.val() - 1, ddlDay.val());

    if ( === "[object Date]") {
        if (isNaN(dobDate.getTime())) {
            // date is not valid
            args.IsValid = false;
            return false;
        else {
            // date is valid
            args.IsValid = true;
            return true;
    else {
        // not a date
        args.IsValid = false;
        return false;

function daysInMonth(month, year) {
    return new Date(year, month, 0).getDate();

Shown below are the dropdownlists, together with their custom validators.

<asp:dropdownlist id="ddlTheDay" visible="true" runat="server" name="ddlTheDay" class="ddlTheDay" />
<asp:dropdownlist id="ddlTheMonth" visible="true" runat="server" name="ddlTheMonth" class="ddlTheMonth" />
<asp:dropdownlist id="ddlTheYear" visible="true" runat="server" name="ddlTheYear" class="ddlTheYear" />
<asp:customvalidator id="cvTheDay" runat="server" SetFocusOnError="True"
Display="Dynamic" ErrorMessage="The date is invalid!" ControlToValidate="ddlTheDay" ClientValidationFunction="validateDate" />
<asp:customvalidator id="cvTheMonth" runat="server" SetFocusOnError="True"
Display="Dynamic" ErrorMessage="The date is invalid!" ControlToValidate="ddlTheMonth" ClientValidationFunction="validateDate" />
<asp:customvalidator id="cvTheYear" runat="server" SetFocusOnError="True"
Display="Dynamic" ErrorMessage="The date is invalid!" ControlToValidate="ddlTheYear" ClientValidationFunction="validateDate" />
<div class="validateDate validDate">The date is invalid!</div>

As can be seen above I am using just the one div with the error announcement. Its default setting is within the module’s CSS file module.css, details are below: