iCalendar Synchronizer for Windows Mobile

Introduction

The article describes a simple implementation of an application for Windows Mobile, that can synchronize the calendar with an external provider (in this case, Google) able to provide the events in iCalendar format.

Background

iCalendar is a file format which allows to exchange event/meeting requests and tasks. The standard shares files with an extension of .ics. Recipients of the iCalendar data file can respond to the sender easily or counter propose another meeting date/time. A very simple event on iCalendar should be:

BEGIN:VCALENDAR
VERSION:2.0
BEGIN:VEVENT
DTSTART:200714T170000Z
DTEND:20070715T035959Z
SUMMARY: Dinner with my father
END:VEVENT
END:VCALENDAR

The standard is based on RFC 2445.

Using the Code

The code is based on the iCalendar parser developed by J. Tim Spurway and adapted to the Windows Mobile and Microsoft Compact Framework .NET 3.5. The application has been developed in C#.

The main steps to develop the system are:

implementing the Emitter to receive events
synchronizing events with Outlook calendar and
implementing the User Interface

The following sequence diagram shows the entire application. When the user calls the "Sync" method implemented by "Form", the system makes an HTTP Request and then parses the iCalendar stream flushed by the server. The "Parser" (implemented by J. Tim Spurway and Robert Prouse) passes a token found to the implemented "IEmitter" interface. In our case, we implemented the IEmitter by OutlookCalendarEmitter which accesses the Outlook Calendar and pushes Appointment into the database.

Implementing the Emitter to Receive Events

"IEmitter" is a simple interface able to receive from the "Parser" class events and attributes from an iCalendar stream source :

class OutlookCalendarEmitter : IEmitter
{
	//local cache
	DateTime start = DateTime.Now;
	DateTime end = DateTime.Now;
	string summary = "";

	//temp var
	string currentTag = "";
	string currentValue = "";
	string currentComponent = "";
	...

	public void doEndComponent()
	{
		Debug.WriteLine("doEndComponent: currentTag=" + currentTag);
		if (currentComponent.Equals("Vevent"))
		{
		AddAppointment(summary, summary, start, end);
		}
	}

	public void doID(Token t)
	{
		Debug.WriteLine("doID: \t" + t.TokenText);
		currentTag = t.TokenText;
	}

	public void doValueProperty(Token t, Token iprop)
	{
		if (iprop != null)
		{
			Debug.WriteLine(t.TokenText + " " + iprop.TokenText);
			currentTag = t.TokenText;
			currentValue = iprop.TokenText;
		}
		else
		{
			currentValue = t.TokenText;
		}
	}


	public void doRest(Token t, Token id)
	{
		doPrepare(id.TokenText, t.TokenText);
	}
}

When the "doEndComponent()" is called for a "VEvent", you can add an appointment on the pocket PC Calendar calling:

AddAppointment(summary, summary, start, end);

Interfacing Microsoft Outlook Pocket Calendar

Now it's time to implement the "AddAppointment(summary, summary, start, end);" method. We need to access the "OutlookSession" and put on the "Appointments" the new event.

class OutlookCalendarEmitter : IEmitter
{
        string formatDate = "yyyyMMdd'T'HHmmss'Z'";
        CultureInfo culture = CultureInfo.InvariantCulture;

        OutlookSession session = new OutlookSession();

        ...
		private void AddAppointment
		  (String subject, String text, DateTime start, DateTime end)
		{
			Debug.WriteLine("Appointment");
			Appointment a = null;
			for (int i = 0; i < session.Appointments.Items.Count; i++)
			{
				Appointment app = session.Appointments.Items[i];
				if (app.Subject.Equals(subject))
				{
					a = app;
					break;
				}
			}

			if (a==null) a=session.Appointments.Items.AddNew();

			a.Subject = subject;
			a.Body = text;
			a.Start = start;
			a.End = end;
			a.Subject = subject;
			a.Update();
                  }
}

Developing the User Interface

In Visual Studio, create a new form such as figure 1:

On the "Sync Now" button, call (double click) the "Sync" method.

private WebRequest req = null;
private OutlookCalendarEmitter emitter = new OutlookCalendarEmitter();
private void DoSync()
{
    string urlText = this.textBoxUrl.Text;
    try
    {
        req = WebRequest.Create(urlText);

        req.Method = "GET";

        TextReader reader = new StreamReader(req.GetResponse().GetResponseStream());

        Parser parser = new Parser(reader, emitter);
        parser.Parse();
    }
    catch (Exception e)
    {
        this.listBox1.Items.Add("Error: " + e.Message);
    }
    req = null;
}

Project

In the attached code, you can find iparser developed by J. Tim Spurway, the user interface and the cabinet project to distribute it. The application was tested on Treo 750.