private void SavePreference()
        {
            XmlElement pref = _project.Preference;

            foreach (XmlNode node in pref.SelectNodes("Property[@Name='ProxyDeploy']"))
            {
                pref.RemoveChild(node);
            }

            XmlHelper  h = new XmlHelper(pref);
            XmlElement p = h.AddElement(".", "Property");

            p.SetAttribute("Name", "ProxyDeploy");

            XmlHelper ph = new XmlHelper(p);

            foreach (DataGridViewRow row in dgSites.Rows)
            {
                if (row.IsNewRow)
                {
                    continue;
                }

                XmlElement t = row.Tag as XmlElement;
                if (t == null)
                {
                    continue;
                }

                ph.AddElement(".", t);
            }

            _project.UpdateProjectPreference(pref);
        }