SharePoint 读取 Site Columns 的数据并绑定到DropdownList

public void GetSiteColumns(DropDownList ddl, String siteColumn)
        {
            var fields = new SPSite(ProjectContent.SiteUrlMapping).RootWeb.Fields;
            var projectCodeXml = fields.TryGetFieldByStaticName(siteColumn).SchemaXml;
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(projectCodeXml);
            XmlNode xn = xmlDoc.SelectSingleNode("Field/CHOICES");
            foreach (var xnl in xn)
            {
                XmlElement xe = (XmlElement)xnl;
                ddl.Items.Add(xe.InnerText);
            }
        }