Last Updated: 08 Jan 2020 12:20 by ADMIN
Release R1 2020

This bug started happening in version Telerik 2019.3.917, and is still present in Telerik 2019.3.1023.

The reproduction is extremely basic:

<table runat="server">
            <telerik:RadMonthYearPicker ID="MonthYear" runat="server" Width="150px">
            <asp:Button ID="btnGenerate" runat="server" Text="Get Report" OnClick="btnGenerate_Click" />

 protected void Page_Load(object sender, EventArgs e)
        if (!IsPostBack)
            MonthYear.SelectedDate = DateTime.Today;
            MonthYear.MaxDate = DateTime.Today.AddDays(1);

When i select a month/date from the control and submit the page i'm getting this script error:

The page freezes and i can get this error in Chrome from browser right-click->inspect->Console tab

Uncaught Sys.ArgumentUndefinedException: Sys.ArgumentUndefinedException: Value cannot be undefined.
Parameter name: handler
    at Function.Error$create [as create] (
    at Object.Sys._errorArgument (
    at Function.Error$argumentUndefined [as argumentUndefined] (
    at Function$_validateParameterType [as _validateParameterType] (
    at Function$_validateParameter [as _validateParameter] (
    at Function$_validateParams [as _validateParams] (
    at EventHandlerList$removeHandler [as removeHandler] (
    at Telerik.Web.UI.RadMonthYearPicker.remove_popupClosed (
    at Telerik.Web.UI.RadMonthYearPicker.dispose (
    at _Application$disposeElement [as disposeElement] (

You can see at the base of the call stack that the RadMonthYearPicker control is referenced. 

Last Updated: 02 Oct 2019 14:28 by ADMIN
Please see demo:

1. tab to calendar button

2. hit enter to open calendar dialog

3. press tab

Notice that instead of causing the focus to move within the calendar pop-up, focus first shifts through all remaining elements of the underlying page. This make this control difficult for users relying solely on keyboard navigation.

Ideally this control should function more like the standard calendar controls, obtaining focus when opened and returning focus to the date field when closed.