For appointment class, we have to use this namespace,

using Microsoft.WindowsMobile.PocketOutlook;

Those below codings are written in one button event

Appointment newappoinment = new Appointment();
newappoinment.Subject = textBox1.Text;
//newappoinment.Start = DateTime.Now;
newappoinment.Start = new DateTime(2007, 02, 10, 12, 00, 00);
//newappoinment.Duration = new TimeSpan(01, 00, 00);
newappoinment.Location = textBox2.Text;
newappoinment.End = new DateTime(2007, 02, 10, 15, 00, 00);
newappoinment.ReminderVibrate = true;
newappoinment.ReminderSound = true;
newappoinment.ReminderRepeat = true;
newappoinment.ReminderSet = true;
using (OutlookSession session = new OutlookSession())
{
session.Appointments.Items.Add(newappoinment);
session.Dispose();
}
MessageBox.Show("Appoinment is fixed");