ASP.NET

VB.net
Protected Sub Calendar1_DayRender(ByVal sender As Object, _
        ByVal e As DayRenderEventArgs) Handles Calendar1.DayRender
    Dim myAppointment As Date = New Date(2005, 10, 1)
    If (e.Day.Date = myAppointment) Then
        e.Day.IsSelectable = True
    Else
        e.Day.IsSelectable = False
    End If
End Sub
 


C#  
protected void Calendar1_DayRender(object sender, 
    DayRenderEventArgs e)
{
    DateTime myAppointment = new DateTime(2005, 10, 1);
    if (e.Day.Date == myAppointment)
    {
        e.Day.IsSelectable = true;
    }
    else
    {
        e.Day.IsSelectable = false; 
    }
}