/// <summary>
        /// Returns the CalDavElement from server with the provided relative url on the server.
        /// </summary>
        /// <param name="url">Relative Url to concrete .ics.</param>
        /// <returns>Found CalDavElement.</returns>
        private CalDavElement GetSingleItemFromServer(String url)
        {
            WebHeaderCollection headers = new WebHeaderCollection();

            headers.Add("Depth", "1");
            headers.Add("Prefer", "return-minimal");
            XmlDocument ResponseXmlDoc;
            String      query = "<c:calendar-multiget xmlns:d=\"DAV:\" xmlns:c=\"urn:ietf:params:xml:ns:caldav\">" +
                                "<d:prop>" +
                                "<d:getetag />" +
                                "<c:calendar-data />" +
                                "</d:prop>" +
                                "<d:href>" + url + "</d:href>" +
                                "</c:calendar-multiget>";

            ResponseXmlDoc = this.QueryCaldavServer("REPORT", headers, query, "application/xml", null);
            List <CalDavElement> responseListCalDav = XmlCalDavParser.Parse(ResponseXmlDoc);

            return(responseListCalDav.First());
        }
        /// <summary>
        /// Returns all CalDavElements from server with full details.
        /// </summary>
        /// <returns>List with all CalDavElements with full details.</returns>
        private List <CalDavElement> GetAllItemsFromServer()
        {
            WebHeaderCollection headers = new WebHeaderCollection();

            headers.Add("Depth", "1");
            headers.Add("Prefer", "return-minimal");
            XmlDocument ResponseXmlDoc;
            string      query = "<c:calendar-query xmlns:d=\"DAV:\" xmlns:c=\"urn:ietf:params:xml:ns:caldav\">" +
                                "<d:prop>" +
                                "<d:getetag />" +
                                "<c:calendar-data />" +
                                "</d:prop>" +
                                "<c:filter>" +
                                "<c:comp-filter name=\"VCALENDAR\">" +
                                "   <c:comp-filter name=\"VEVENT\" />" +
                                "</c:comp-filter>" +
                                "</c:filter>" +
                                "</c:calendar-query>";

            ResponseXmlDoc = this.QueryCaldavServer("REPORT", headers, query, "application/xml", null);
            List <CalDavElement> responseListCalDav = XmlCalDavParser.Parse(ResponseXmlDoc);

            return(responseListCalDav);
        }