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The OnCalendarViewChanging client-side event handler of the ASP NET AJAX Calendar is called when the calendar navigates to a new view, before the viewable area rendered by the calendar is changed.

The event handler receives two arguments:

  1. the RadCalendar object that fired the event.

  2. an event arguments object that exposes the following methods:OnCalendarViewChanging event arguments object

Name Return Type Arguments Description
get_step() int Returns the number of views by which the calendar is about to change.
set_cancel(value) bool Lets you prevent the view from changing.

This event can be used to pre-process some conditions or visual styles and content before the final rendering of the calendar. The following example uses the OnCalendarViewChanging event to prevent the view from changing unless a date in the current month is selected:

<telerik:RadCalendar RenderMode="Lightweight" ID="RadCalendar1" runat="server" ShowOtherMonthsDays="False" >
    <ClientEvents OnCalendarViewChanging="checkSelections" />
function checkSelections(sender, eventArgs) {
    var selDates = sender.get_selectedDates();
    var focus = sender.get_focusedDate();
    var viewHasSelection = false;

    for (var i = 0; i < selDates.length; i++) {
        if ((selDates[i][0] == focus[0]) && (selDates[i][1] == focus[1])) {
            viewHasSelection = true;


    if (eventArgs.get_cancel()) {
        alert("You must select a value before moving " + (eventArgs.get_step() > 0 ? "forward " : "back ") + "to another month.");

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