Hello,

You can disable specific dates by setting the DropDownCalendarID to the ID of a WebMonthCalendar and handle its RenderDay client-side event. Inside it the day should be checked and depending on its day of week number (dow property), the day should be set to disabled. It could be done with the following markup and JavaScript code:

 <ig:WebDatePicker ID="WebDatePicker1" runat="server" DropDownCalendarID="WebMonthCalendar1">
</ig:WebDatePicker>
 <ig:WebMonthCalendar ID="WebMonthCalendar1" runat="server">
        <ClientEvents RenderDay="RenderDay" />
 </ig:WebMonthCalendar>

function RenderDay(sender, e) {
           //disable all dates that are different from Mondat/Wednessday/Friday
            if (e.get_day().dow != 1 && e.get_day().dow != 3 && e.get_day().dow != 5) {
                e.get_day().set_disabled(true);
            } 

Please let me know if you have any questions.

Regards,
Ivan Kitanov