The Message property can contain a value by default in some circumstances; for example, if an appointment's Appointment.StartDateTime or Appointment.EndDateTime property is outside the range defined by the associated CalendarInfo's LogicalDayOffset and LogicalDayDuration properties. Listeners can set the Message property to an empty string to prevent the message from being displayed to the end user.
The Message property can be set to any non-empty string value, which is then displayed in a MessageBox, regardless of whether any of the AppointmentDialog's fields contain invalid values.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2