WebDav & Exchange: Create appointment, avoid overwrite existing one

The destination URL doesn't need to be based on the subject, Exchange just does that by default, and adds incrementing numbers to the end if required.  The easiest thing to do is to create a unique URL based on the date and time, and then add a random number on the end.  You will end up with something like

http://server/exchange/user/calendar/20070910-140625-86527.eml

Thanks LeeDerbyshire
I thought of that too.. but I just want to keep having subjects as filenames, just as Exchange does.
It is also easier to find the item in Exchange Explorer.
Do you know how to check if that URL already exists?

Do a GET to the URL.  If you get a 404 response, then it doesn't exist.  A 200 means OK, and it does exist.  If it exists, then add something unique to the end.

Sounds good :-D
How exactly do I "do a GET"?

Well, to create the appointments, I guess you are using a WinHTTPRequest object, or something similar, to send a PROPPATCH request? To see if something exists, try sending a GET instead, and look at the status of the response.  Maybe you could show the code you are using to create the appointments?

Actually I don't understand my code at all... I couldn't find any tutorial about webdav

                PROPPATCHRequest = (System.Net.HttpWebRequest)HttpWebRequest.Create(
                    strCalendarUri + strApptItem); // this is the URL http://....eml
                PROPPATCHRequest.Credentials = MyCredentialCache;
                PROPPATCHRequest.Method = "PROPPATCH";
                bytes = Encoding.UTF8.GetBytes((string)strApptRequest); // strApptRequest is the xml
                PROPPATCHRequest.ContentLength = bytes.Length;
                PROPPATCHRequestStream = PROPPATCHRequest.GetRequestStream();
                PROPPATCHRequestStream.Write(bytes, 0, bytes.Length);
                PROPPATCHRequestStream.Close();
                PROPPATCHRequest.ContentType = "text/xml";
                PROPPATCHResponse = (System.Net.HttpWebResponse)PROPPATCHRequest.GetResponse(); // Create the appointment in the Calendar folder of the user's mailbox.
                PROPPATCHResponse.Close();

Thank you LeeDerbyshire

Thanks LeeDerbyshire it's close. I got it working

                try
                {
                    string originalName = strApptItem;
                    for(int n=1; n<=1000; n++)
                    {
                        GETRequest = (System.Net.HttpWebRequest)HttpWebRequest.Create(strCalendarUri + strApptItem);
                        GETRequest.Credentials = MyCredentialCache;
                        GETRequest.Method = "GET";
                        GETResponse = (System.Net.HttpWebResponse)GETRequest.GetResponse();
                        GETResponse.Close();
                        strApptItem = originalName + n.ToString();
                    }
                }
                catch (Exception ex)
                {
                    if (ex.Message.IndexOf("(404)") == -1)
                        throw ex;
                }

I don't assume it exists because all subjects are going to contain unique IDs... But just in case... =P