xml字符串转为XmlDocument

string xml = "<xml><logistics_express_get_respose><express_detail><company_code><![CDATA[ZTO]]></company_code>";
        xml += "<express_no><![CDATA[201001038546]]></express_no>";
        xml += "<trace_list>";
        xml += "<transit_step_info><status_time><![CDATA[2011-06-04 21:21:00]]></status_time><status_desc><![CDATA[广州华都   派件已签收,签收人是 杨婉清]]></status_desc></transit_step_info>";
        xml += "<transit_step_info><status_time><![CDATA[2011-06-04 21:21:00]]></status_time><status_desc><![CDATA[上海浦东新区中转站]]></status_desc></transit_step_info>";
        xml += " </trace_list><status><![CDATA[对方已签收]]></status>";
        xml += "</express_detail></logistics_express_get_respose></xml>";
        System.Xml.XmlDocument DOM = new System.Xml.XmlDocument();
        DOM.LoadXml(xml);