Displaying the Popup
By default, RadMonthYearPicker control displays popup button to the left of the input area. When the user clicks on the button, the embedded MonthYearView pops up to aid in selecting a value. This behavior happens automatically, without any programming on your part.
To alter this behavior, you can hide the DatePopupButton of the RadMonthYearPicker control and display the popup control when the user interacts with the DateInput. You need to set the DatePopupButton.Visible property to false and ShowPopupOnFocus to true.
<telerik:RadMonthYearPicker RenderMode="Lightweight" ID="RadMonthYearPicker1" runat="server" ShowPopupOnFocus="true">
<DatePopupButton Visible="false" />
</telerik:RadMonthYearPicker>
Alternatively you can use client-side code. The client-side showPopup() method displays the popup MonthYearView control. The following example illustrates how to hide the popup buttons and use client-side code to display the popup.
<telerik:RadMonthYearPicker RenderMode="Lightweight" ID="RadMonthYearPicker1" runat="server" DatePopupButton-Visible="false">
<DateInput>
<ClientEvents OnFocus="showMontYearPopup" />
</DateInput>
</telerik:RadMonthYearPicker>