Sample Exchange Usage of MyAppointment class described in blog post http://anlai.wordpress.com/2011/06/22/exchange-calendar-syncing-with-exchange-web-services-ews-api/

ExchangeFunctions.cs

public class ExchangeFunctions
{
	private const string _username = "uname";
	private const string _password = "password";
	private const string _domain = "domain";

	public static string CreateAppointment(string mailboxId, MyAppointment appt)
	{
		var service = new ExchangeService(ExchangeVersion.Exchange2007_SP1);
		service.Credentials = new WebCredentials(_username, _password, _domain);

		// auto loads the url for the targetted mailbox
		service.AutodiscoverUrl(mailboxId);

		var appointment = ConvertAppointment(service, appt);
		
		// save the appointment, bound to the targetted user's mailbox, using delegate permissions
		appointment.Save(new FolderId(WellKnownFolderName.Calendar, mailboxId));
	}
	
	// Convert My Appointment to Exchange Appointment class
	private Appointment ConvertAppointment(ExchangeService service, MyAppointment appt)
	{
		// create the appointment
		var appointment = new Appointment(service);
		appointment.Subject = appt.Subject;
		appointment.Body = appt.Body;
		appointment.Start = appt.Begin;
		appointment.End = appt.End;
		appointment.LegacyFreeBusyStatus = appt.Busy ? LegacyFreeBusyStatus.Busy : LegacyFreeBusyStatus.Free;
		
		return appointment;
	}
}

Main.cs

function void Main()
{
	var appt = new MyAppointment()
	{
		Start = DateTime.Now(),
		End = DateTime.Now().AddMinutes(30),
		Subject = "Sample 1",
		Body = "Sample 1 Body",
		Busy = true
	};
	
	CreateAppt("mailboxid", appt);
}

MyAppointment.cs

public class MyAppointment
{
    public int Id { get; set; }
    public DateTime Start { get; set; }
    public DateTime End { get; set; }
    public string Subject { get; set; }
    public string Body { get; set; }
	public string Busy { get; set; }
 
    public string ExchangeId { get; set; }
}