Exchange Web Services find item by unique id - asp.net

Question

I just started using Microsoft Exchange Web Services for the first time. Want I want to be able to do is the following:
Create Meeting
Update Meeting
Cancel/Delete Meeting
These meetings are created in an ASP.NET MVC application and saved into a SQL Server database. I simply wish to integrate this with the on site Exchange Server. So far, I'm able to created my meeting with the following code:
public static Task<string> CreateMeetingAsync(string from, List<string> to, string subject, string body, string location, DateTime begin, DateTime end)
{
var tcs = new TaskCompletionSource<string>();
try
{
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2013);
service.Credentials = CredentialCache.DefaultNetworkCredentials;
//service.UseDefaultCredentials = true;
// I suspect the Service URL needs to be set from the user email address because this is then used to set the organiser
// of the appointment constructed below. The Organizer is a read-only field that cannot be manually set. (security measure)
service.AutodiscoverUrl(from);
//service.Url = new Uri(WebConfigurationManager.AppSettings["ExchangeServer"]);
Appointment meeting = new Appointment(service);
meeting.Subject = subject;
meeting.Body = "<span style=\"font-family:'Century Gothic'\" >" + body + "</span><br/><br/><br/>";
meeting.Body.BodyType = BodyType.HTML;
meeting.Start = begin;
meeting.End = end;
meeting.Location = location;
meeting.ReminderMinutesBeforeStart = 60;
foreach (string attendee in to)
{
meeting.RequiredAttendees.Add(attendee);
}
meeting.Save(SendInvitationsMode.SendToAllAndSaveCopy);
tcs.TrySetResult(meeting.Id.UniqueId);
}
catch (Exception ex)
{
tcs.TrySetException(ex);
}
return tcs.Task;
}
This successfully creates my meeting, places it into the user's calendar in outlook and sends a meeting request to all attendees. I noticed the following exception when attempting to call meeting.Save(SendInvitationsMode.SendToAllAndSaveCopy); twice:
This operation can't be performed because this service object already has an ID. To update this service object, use the Update() method instead.
I thought: Great, it saves the item in exchange with a unique id. I'll save this ID in my application's database and use it later to edit/cancel the meeting. That is why I return the id: tcs.TrySetResult(meeting.Id.UniqueId);
This is saved nicely into my application's database:
Now, I am attempting to do the next part where I update the meeting, but I cannot find a way to search for the item based on the unique identifier that I'm saving. An example I found on code.msdn uses the service.FindItems() method with a query that searches the subject:
string querystring = "Subject:Lunch";
FindItemsResults<Item> results = service.FindItems(WellKnownFolderName.Calendar, querystring, view);
I don't like this. There could be a chance that the user created a meeting outside of my application that coincidentally has the same subject, and here come's my application and cancel's it. I tried to determine wether it's possible to use the unique id in the query string, but this does not seem possible.
I did notice on the above query string page that the last property you can search on is (property is not specified) that searches in "all word phase properties.". I tried thus simply putting the id into the query, but this returns no results:
FindItemsResults<Item> results = service.FindItems(WellKnownFolderName.Calendar, "AAMkADJhZDQzZWFmLWYxYTktNGI1Yi1iZTA5LWVmOTE3MmJiMGIxZgBGAAAAAAAqhOzrXRdvRoA6yPu9S/XnBwDXvBDBMebkTqUWix3HxZrnAAAA2LKLAAB5iS34oLxkSJIUht/+h9J1AAFlEVLAAAA=", view);

Answer 1

Use the Appointment.Bind static function, providing a service object and the ItemId saved in your database. Be aware with meeting workflow (invite, accept, reject) can re-create a meeting on the same calendar with a new ItemId. But if you are just looking at the meeting you make on your own calendar, you should be OK.