Exchange Web Services find item by unique id

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);

pjneary pjneary · Accepted Answer · 2016-03-18T21:52:18

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.

Exchange Web Services find item by unique id

1 Answers