ASP.NET Calendar - Tutorial - Select only special dates

Calendar can have unlimited number of special dates.
For each special date you can set CSS class name and a ToolTip.

 

Special dates are marked in red.
Only special dates are selectable.

ASP.NET

<obout:Calendar runat="server" AllowSelectSpecial="true" EnabledDateExpression="false">
    <obout:SpecialDate Year="2006" Month="3" Day="20"
         ToolTip="Dentist appointment" />
    <obout:SpecialDate Year="-1" Month="7" Day="4"
         ToolTip="Independence Day" CSSClass="indDay" CSSClassOver="indDay" />
</obout:Calendar>

C#

Use AddSpecialDate method. See documentation for details on this method.
Cal.AddSpecialDate(2006, 3, 20, "Dentist Appointment");
Cal.AddSpecialDate(-1, 7, 4, "Independence Day", "indDay");