Asp.net Ajax Calendar Extender and Past Date Validation Javascript ...

When using asp.net ajax calendar extender, we want to restrict users from selecting dates in the past.So to achieve that we have to make use of OnClientDateSelectionChanged  event of calendarextender.Below is the code.

    <script language=”javascript” type=”text/javascript”>

    function CheckForPastDate(sender, args) {

    var selectedDate = new Date();

    selectedDate = sender._selectedDate;

    var todayDate = new Date();

    if (selectedDate.getDateOnly() < todayDate.getDateOnly()) {

    sender._selectedDate = todayDate;                  sender._textbox.set_Value(sender._selectedDate.format(sender._format));

    alert(“Date Cannot be in the past”);

    }

    }

    </script>

    <asp:TextBox ID=”txtDate” contentEditable=”false” runat=”server” CssClass=”txtcss”></asp:TextBox>&nbsp;

    <asp:Image ID=”imgCal” runat=”server” ImageUrl=”~/img/calendar.gif” />

    <cc1:CalendarExtender ID=”CalExtDate” runat=”server” FirstDayOfWeek=”Sunday” PopupButtonID=”imgCal”PopupPosition=”BottomLeft” Format=”dd/MM/yyyy” OnClientDateSelectionChanged=”CheckForPastDate” TargetControlID=”txtDate”>

    </cc1:CalendarExtender>

 Original Source:
http://pankajlalwani.wordpress.com/2009/12/23/asp-net-ajax-calendar-extender-and-past-date-validation-javascript/