IEnumerable<string> grandChildData =

                from el in StreamRootChildDoc(new StringReader(markup))

                where (int)el.Attribute("Key") > 1

                select (string)el.Element("GrandChild");

            foreach (string str in grandChildData)

            {

                Console.WriteLine(str);

            }

 

处理函数

 static IEnumerable<XElement> StreamRootChildDoc(StringReader stringReader)

        {

            using (XmlReader reader = XmlReader.Create(stringReader))

            {

                reader.MoveToContent();

                // Parse the file and display each of the nodes.

                while (reader.Read())

                {

                    switch (reader.NodeType)

                    {

                        case XmlNodeType.Element:

                            if (reader.Name == "Child")

                            {

                                XElement el = XElement.ReadFrom(reader) as XElement;

                                if (el != null)

                                    yield return el;

                            }

                            break;

                    }

                }

            }

        }