Linq to Xml

1.使用LINQ 访问XML
　　• 更好的操作XML
　　• 支持语言集成查询
　　• 更方便、更快速、更简单、更智能的XML API
2.LINQ to XML
　　• LINQ to XML 是一种启用了LINQ 的内存XML 编程接口，使用它，可以在.NET Framework 编程语言中处理XML。
　　• 它将XML文档置于内存中这一点很像文档对象模型(DOM) 。
　　• 它提供一种新的对象模型，这是一种更轻量的模型，使用也更方便，这种模型利用了Visual C# 2008 在语言方面的改进。

3.XElement 类 
　　• 它表示一个XML 元素
　　• 可以使用该类
　　　　– 创建元素
　　　　– 更改元素内容 内
　　　　– 添加、更改或删除子元素
　　　　– 向元素中添加属性
　　　　– 以文本格式序列化元素内容
　　• 可以与System Xml中的其他类（例如 可以与System.Xml 中的其他类（例如XmlReader、XmlWriter 和XslCompiledTransform）进行互操作
4.XAttribute 类 
　　• 属性是与元素关联的名称/值对
　　• XAttribute类表示XML属性 XAttribute类表示XML 属性
　　• 属性集合的LINQ 查询表达式与元素集合的LINQ 查询表达式看起来非常相似
5.XDocument 类 
　　• XDocument 类包含有效的 XML 文档所需的信息。其中包括XML 声明、处理指令和注释。
　　• 如果需要XDocument类提供的特定功能，您只需创建XDocument对象。在很多情况下，可以直接使用Xelement。
　　　　直接使用XElement是一种比较简单的编程模型。
　　• XDocument 是从XContainer派生的。因此，它可以包含子节点.但是，XDocument对象只能有一个子XElement节点。
　　　　这反映了XML 标准，即在XML文档中只能有一个根元素。

6.构造XML树
　　• “函数构造”方法
　　　　– 通过将查询结果用作XElement 和XAttribute 对象构造函数的参数，实现了一种功能强大的
　　　　　　创建XML 树的方法。
　　　　– 利用这种方法，开发人员可以方便地将 XML 树从一种形状转换为另一种形状。 
　　• 分析字符串
　　• 从文件加载
7.序列化XML树
　　•XML 树可以序列化为
　　　　– 字符串
　　　　– File
　　　　– TextWriter
　　　　– XmlWriter
　　　　– XmlReader

8.查询与转换XML树
　　• 基本查询
　　• 使用LINQ查询操作符查询
　　• 转换XML格式
　　• 将集合、数据转换成XML
　　• 转换成其它数据格式 
9.修改XML树
　　• 内存中XML 树修改与函数构造
　　• 向XML树中添加元素、属性和节点
　　• 修改XML 树中的元素、属性和节点
　　• 从XML 树中移除元素、属性和节点
　　• 维护名称/值对 
　　• 更改整个XML 树的命名空间

代码如下: 

    class Program
    {
        static void Main(string[] args)
        {
            //构造 XML 树
            //BuildXmlTreeUsingDom();
            //BuildXmlTree();
            //BuildXmlTreeWithLINQ();
            //BuildXmlTreeWithAttributes();
            //BuildXmlDocument();
            //ParseXml();
            //LoadXmlFromFile();
            //CatchException();
            //CreateXElementUsingXmlReader();

            //序列化 XML 树
            //SerializeToFile1();
            //SerializeToFile2();
            //SerializeToXmlReader();

            //查询 XML
            //QueryElements();
            //QueryElements2();
            //QueryAttributes();

            //使用 LINQ 查询操作符进行查询
            //LINQQuery1();
            //LINQQuery2();
            //LINQQuery3();
            //LINQQuery4();
            //LINQQuery5();

            //转换
            //XmlTransform1();
            //XmlTransform2();
            //XmlTransform3();

            //修改 XML 树
            //ModifyXml1();
            //ModifyXml2();
            //ModifyXml3();
            //ModifyXml4();
        }

        private static void SerializeToXmlReader()
        {
            string xslMarkup = @"<?xml version='1.0'?>
                <xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
                    <xsl:template match='/Parent'>
                        <Root>
                            <C1>
                            <xsl:value-of select='Child1'/>
                            </C1>
                            <C2>
                            <xsl:value-of select='Child2'/>
                            </C2>
                        </Root>
                    </xsl:template>
                </xsl:stylesheet>";

            XDocument xmlTree = new XDocument(
                new XElement("Parent",
                    new XElement("Child1", "Child1 data"),
                    new XElement("Child2", "Child2 data")
                )
            );

            XDocument newTree = new XDocument();
            using (XmlWriter writer = newTree.CreateWriter())
            {
                // Load the style sheet.
                XslCompiledTransform xslt = new XslCompiledTransform();
                xslt.Load(XmlReader.Create(new StringReader(xslMarkup)));

                // Execute the transformation and output the results to a writer.
                xslt.Transform(xmlTree.CreateReader(), writer);
            }

            Console.WriteLine(newTree);

        }

        private static void SerializeToFile2()
        {
            StringBuilder sb = new StringBuilder();
            XmlWriterSettings xws = new XmlWriterSettings();
            xws.OmitXmlDeclaration = true;

            using (XmlWriter xw = XmlWriter.Create(sb, xws))
            {
                XElement root = new XElement("Root",
                    new XElement("Child", "child content")
                );
                root.Save(xw);
            }
            Console.WriteLine(sb.ToString());

        }

        private static void SerializeToFile1()
        {
            XElement root = new XElement("Root",
                new XElement("Child", "child content")
            );
            root.Save("Root.xml");
            string str = File.ReadAllText("Root.xml");
            Console.WriteLine(str);

        }

        private static void ModifyXml4()
        {
            // Create an element with no content.
            XElement root = new XElement("Root");

            // Add a number of name/value pairs as attributes.
            root.SetAttributeValue("Top", 22);
            root.SetAttributeValue("Left", 20);
            root.SetAttributeValue("Bottom", 122);
            root.SetAttributeValue("Right", 300);
            root.SetAttributeValue("DefaultColor", "Color.Red");
            Console.WriteLine(root);

            // Replace the value of Top.
            root.SetAttributeValue("Top", 10);
            Console.WriteLine(root);

            // Remove DefaultColor.
            root.SetAttributeValue("DefaultColor", null);
            Console.WriteLine(root);

        }

        private static void ModifyXml3()
        {
            XElement root = XElement.Parse(@"<Root>
                <Child1>
                    <GrandChild1/>
                    <GrandChild2/>
                    <GrandChild3/>
                </Child1>
                <Child2>
                    <GrandChild4/>
                    <GrandChild5/>
                    <GrandChild6/>
                </Child2>
                <Child3>
                    <GrandChild7/>
                    <GrandChild8/>
                    <GrandChild9/>
                </Child3>
            </Root>");
            root.Element("Child1").Element("GrandChild1").Remove();
            root.Element("Child2").Elements().ToList().Remove();
            root.Element("Child3").Elements().Remove();
            Console.WriteLine(root);

        }

        private static void ModifyXml2()
        {
            XElement srcTree = new XElement("Root",
                new XElement("Element1", 1),
                new XElement("Element2", 2),
                new XElement("Element3", 3),
                new XElement("Element4", 4),
                new XElement("Element5", 5)
            );
            XElement xmlTree = new XElement("Root",
                new XElement("Child1", 1),
                new XElement("Child2", 2),
                new XElement("Child3", 3),
                new XElement("Child4", 4),
                new XElement("Child5", 5)
            );
            xmlTree.Add(new XElement("NewChild", "new content"));
            xmlTree.Add(
                from el in srcTree.Elements()
                where (int)el > 3
                select el
            );
            // Even though Child9 does not exist in srcTree, the following statement will not
            // throw an exception, and nothing will be added to xmlTree.
            xmlTree.Add(srcTree.Element("Child9"));
            Console.WriteLine(xmlTree);

        }

        private static void ModifyXml1()
        {
            XElement root = XElement.Parse("<?xml version=\"1.0\" encoding=\"utf-8\" ?><Root Data1=\"123\" Data2=\"456\"><Child1>Content</Child1></Root>");

            foreach (XAttribute att in root.Attributes())
            {
                root.Add(new XElement(att.Name, (string)att));
            }
            root.Attributes().Remove();
            Console.WriteLine(root);

        }

        private static void XmlTransform3()
        {
            XElement custOrd = XElement.Load("CustomersOrders.xml");
            IEnumerable<Customer> custList =
                from el in custOrd.Element("Customers").Elements("Customer")
                select new Customer(
                    (string)el.Attribute("CustomerID"),
                    (string)el.Element("CompanyName"),
                    (string)el.Element("ContactName")
                );
            foreach (Customer cust in custList)
                Console.WriteLine(cust);

        }

        private static void XmlTransform2()
        {
            XElement co = XElement.Load("CustomersOrders.xml");
            XElement newCustOrd =
                new XElement("Root",
                    from cust in co.Element("Customers").Elements("Customer")
                    select new XElement("Customer",
                        cust.Attributes(),
                        cust.Elements(),
                        new XElement("Orders",
                            from ord in co.Element("Orders").Elements("Order")
                            where (string)ord.Element("CustomerID") == (string)cust.Attribute("CustomerID")
                            select new XElement("Order",
                                ord.Attributes(),
                                ord.Element("EmployeeID"),
                                ord.Element("OrderDate"),
                                ord.Element("RequiredDate"),
                                ord.Element("ShipInfo")
                            )
                        )
                    )
                );
            Console.WriteLine(newCustOrd);

        }

        private static void XmlTransform1()
        {
            Dictionary<string, string> dict = new Dictionary<string, string>();
            dict.Add("Child1", "Value1");
            dict.Add("Child2", "Value2");
            dict.Add("Child3", "Value3");
            dict.Add("Child4", "Value4");
            XElement root = new XElement("Root",
                from keyValue in dict
                select new XElement(keyValue.Key, keyValue.Value)
            );
            Console.WriteLine(root);

        }

        private static void LINQQuery5()
        {
            XElement root = XElement.Load("Data.xml");
            IEnumerable<decimal> extensions =
                from el in root.Elements("Data")
                let extension = (decimal)el.Element("Quantity") * (decimal)el.Element("Price")
                where extension >= 25
                orderby extension
                select extension;
            foreach (decimal ex in extensions)
                Console.WriteLine(ex);

        }

        private static void LINQQuery4()
        {
            XElement root = XElement.Load("Data.xml");
            IEnumerable<decimal> prices =
                from el in root.Elements("Data")
                let price = (decimal)el.Element("Price")
                orderby price
                select price;
            foreach (decimal el in prices)
                Console.WriteLine(el);

        }

        private static void LINQQuery3()
        {
            XElement root = XElement.Parse(@"<Root>
              <Child1>
                <GrandChild1>GC1 Value</GrandChild1>
              </Child1>
              <Child2>
                <GrandChild2>GC2 Value</GrandChild2>
              </Child2>
              <Child3>
                <GrandChild3>GC3 Value</GrandChild3>
              </Child3>
              <Child4>
                <GrandChild4>GC4 Value</GrandChild4>
              </Child4>
            </Root>");
            string grandChild3 = (string)
                (from el in root.Descendants("GrandChild3")
                 select el).First();
            Console.WriteLine(grandChild3);

        }

        private static void LINQQuery2()
        {
            XElement root = XElement.Parse(@"<root>
              <para>
                <r>
                  <t>Some text </t>
                </r>
                <n>
                  <r>
                    <t>that is broken up into </t>
                  </r>
                </n>
                <n>
                  <r>
                    <t>multiple segments.</t>
                  </r>
                </n>
              </para>
            </root>");
            IEnumerable<string> textSegs =
                from seg in root.Descendants("t")
                select (string)seg;

            string str = textSegs.Aggregate(new StringBuilder(),
                (sb, i) => sb.Append(i),
                sp => sp.ToString()
            );

            Console.WriteLine(str);

        }

        private static void LINQQuery1()
        {
            XElement root = XElement.Load("PurchaseOrder.xml");
            IEnumerable<XElement> address =
                from el in root.Elements("Address")
                where (string)el.Attribute("Type") == "Billing"
                select el;
            foreach (XElement el in address)
                Console.WriteLine(el);

        }

        private static void QueryAttributes()
        {
            XElement val = new XElement("Value",
                new XAttribute("ID", "1243"),
                new XAttribute("Type", "int"),
                new XAttribute("ConvertableTo", "double"),
                "100");
            IEnumerable<XAttribute> listOfAttributes =
                from att in val.Attributes()
                select att;
            foreach (XAttribute a in listOfAttributes)
                Console.WriteLine(a);
        }

        private static void QueryElements2()
        {
            XElement purchaseOrders = XElement.Load("PurchaseOrders.xml");
            IEnumerable<XElement> names =
                from el in purchaseOrders
                    .Elements("PurchaseOrder")
                    .Elements("Address")
                    .Elements("Name")
                select el;
            foreach (XElement e in names)
                Console.WriteLine(e);

        }

        private static void QueryElements()
        {
            XElement po = XElement.Load("PurchaseOrder.xml");
            IEnumerable<XElement> childElements =
                from el in po.Elements()
                select el;
            foreach (XElement el in childElements)
                Console.WriteLine("Name: " + el.Name);

        }

        private static void CreateXElementUsingXmlReader()
        {
            XmlReader r = XmlReader.Create("books.xml");
            while (r.NodeType != XmlNodeType.Element)
                r.Read();
            XElement e = XElement.Load(r);
            Console.WriteLine(e);
        }

        private static void CatchException()
        {
            try
            {
                XElement contacts = XElement.Parse(
                    @"<Contacts>
                        <Contact>
                            <Name>Jim Wilson</Name>
                        </Contact>
                      </Contcts>");

                Console.WriteLine(contacts);
            }
            catch (System.Xml.XmlException e)
            {
                Console.WriteLine(e.Message);
            }

        }

        private static void LoadXmlFromFile()
        {
            XElement booksFromFile = XElement.Load(@"books.xml");
            Console.WriteLine(booksFromFile);
        }

        private static void ParseXml()
        {
            XElement contacts = XElement.Parse(
            @"<Contacts>
                <Contact>
                    <Name>Patrick Hines</Name>
                    <Phone Type=""home"">206-555-0144</Phone>
                    <Phone type=""work"">425-555-0145</Phone>
                    <Address>
                    <Street1>123 Main St</Street1>
                    <City>Mercer Island</City>
                    <State>WA</State>
                    <Postal>68042</Postal>
                    </Address>
                    <NetWorth>10</NetWorth>
                </Contact>
                <Contact>
                    <Name>Gretchen Rivas</Name>
                    <Phone Type=""mobile"">206-555-0163</Phone>
                    <Address>
                    <Street1>123 Main St</Street1>
                    <City>Mercer Island</City>
                    <State>WA</State>
                    <Postal>68042</Postal>
                    </Address>
                    <NetWorth>11</NetWorth>
                </Contact>
            </Contacts>");
            Console.WriteLine(contacts);
        }

        private static void BuildXmlDocument()
        {
            XDocument d = new XDocument(
                new XComment("This is a comment."),
                new XProcessingInstruction("xml-stylesheet",
                    "href='mystyle.css' title='Compact' type='text/css'"),
                new XElement("Pubs",
                    new XElement("Book",
                        new XElement("Title", "Artifacts of Roman Civilization"),
                        new XElement("Author", "Moreno, Jordao")
                    ),
                    new XElement("Book",
                        new XElement("Title", "Midieval Tools and Implements"),
                        new XElement("Author", "Gazit, Inbar")
                    )
                ),
                new XComment("This is another comment.")
            );
            d.Declaration = new XDeclaration("1.0", "utf-8", "true");
            Console.WriteLine(d);

            d.Save("test.xml");
        }

        private static void BuildXmlTreeWithAttributes()
        {
            XElement c = new XElement("Customers",
                new XElement("Customer",
                    new XElement("Name", "John Doe"),
                    new XElement("PhoneNumbers",
                        new XElement("Phone",
                            new XAttribute("type", "home"),
                            "555-555-5555"),
                        new XElement("Phone",
                            new XAttribute("type", "work"),
                            "666-666-6666")
                    )
                )
            );
            Console.WriteLine(c);

        }

        private static void BuildXmlTreeWithLINQ()
        {
            XElement srcTree = new XElement("Root",
                new XElement("Element", 1),
                new XElement("Element", 2),
                new XElement("Element", 3),
                new XElement("Element", 4),
                new XElement("Element", 5)
            );
            XElement xmlTree = new XElement("Root",
                new XElement("Child", 1),
                new XElement("Child", 2),
                from el in srcTree.Elements()
                where (int)el > 2
                select el
            );
            Console.WriteLine(xmlTree);

        }

        private static void BuildXmlTree()
        {
            XElement contacts =
                new XElement("Contacts",
                    new XElement("Contact",
                        new XElement("Name", "Patrick Hines"),
                        new XElement("Phone", "206-555-0144"),
                        new XElement("Address",
                            new XElement("Street1", "123 Main St"),
                            new XElement("City", "Mercer Island"),
                            new XElement("State", "WA"),
                            new XElement("Postal", "68042")
                        )
                    )
                );
            Console.WriteLine(contacts);
        }

        private static void BuildXmlTreeUsingDom()
        {
            XmlDocument doc = new XmlDocument();
            XmlElement name = doc.CreateElement("Name");
            name.InnerText = "Patrick Hines";
            XmlElement phone1 = doc.CreateElement("Phone");
            phone1.SetAttribute("Type", "Home");
            phone1.InnerText = "206-555-0144";
            XmlElement phone2 = doc.CreateElement("Phone");
            phone2.SetAttribute("Type", "Work");
            phone2.InnerText = "425-555-0145";
            XmlElement street1 = doc.CreateElement("Street1");
            street1.InnerText = "123 Main St";
            XmlElement city = doc.CreateElement("City");
            city.InnerText = "Mercer Island";
            XmlElement state = doc.CreateElement("State");
            state.InnerText = "WA";
            XmlElement postal = doc.CreateElement("Postal");
            postal.InnerText = "68042";
            XmlElement address = doc.CreateElement("Address");
            address.AppendChild(street1);
            address.AppendChild(city);
            address.AppendChild(state);
            address.AppendChild(postal);
            XmlElement contact = doc.CreateElement("Contact");
            contact.AppendChild(name);
            contact.AppendChild(phone1);
            contact.AppendChild(phone2);
            contact.AppendChild(address);
            XmlElement contacts = doc.CreateElement("Contacts");
            contacts.AppendChild(contact);
            doc.AppendChild(contacts);

            Console.WriteLine(doc.OuterXml);
        }
    }

 

10.生成rss

    public class RSSHandler : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            NorthwindDataContext db = new NorthwindDataContext();

            XElement rssRoot = new XElement("rss",
                new XAttribute("version", "2.0"),
                new XElement("channel",
                    new XElement("title", "My RSS Feed"),
                    new XElement("link", "http://www.cnblogs.com/refactor"),
                    new XElement("description", "Northwind Products Feed"),
                    from product in db.Product
                    orderby product.Name descending
                    select new XElement("item",
                           new XElement("title", product.Name),
                           new XElement("link", "p.aspx?id=" + product.ProductID),
                           new XElement("description", "Color: " +
                            product.Color+"<br/>Size:"+product.Size)

                           )
                    )
                );

            context.Response.Write(rssRoot.ToString());
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

    }

 

　　效果图: