string a=  Dal.cs1();          string b = Dal.cs2();          XmlDocument doc1 = new XmlDocument();          doc1.LoadXml(a);          XmlDocument doc2 = new XmlDocument();          doc2.LoadXml(b);          XmlNode aaa1 = doc1.SelectSingleNode("//root");          XmlNode bbb1 = doc2.SelectSingleNode("//root");          XmlDocument xmlDoc = new XmlDocument();                    string aa = "
     
      " + aaa1.InnerXml + "
     ";          string bb = "
     
      " + bbb1.InnerXml + "
     ";          xmlDoc.LoadXml("
     
      " + aa + bb + "
     ");