4.Linq to Xml

目录

1.Linq to Xml函数构造方法

2.创建包含文本节点的Xml文档

3.保存和加载Xml

4.处理Xml片段

5.从数据库中生成XML

1.Linq to Xml函数构造方法

Linq to Xml引入了一种创建xml的方式，叫做函数构建方式（functional construction）,通过这种方式可以以一种类似Xml文档结构的方式快速构建XML。

            //使用Linq To XML 函数构建方式创建XML文档
            XDocument xdoc = new XDocument(
                new XElement("customers",
                    new XElement("customer",
                        new XAttribute("ID", "A"),
                        new XAttribute("City", "New York"),
                        new XAttribute("Region", "USA"),
                        new XElement("order",
                            new XAttribute("Item", "Widget"),
                            new XAttribute("Price", )
                        ),
                        new XElement("order",
                            new XAttribute("Item", "Tire"),
                            new XAttribute("Price", )
                        )
                    ),
                    new XElement("customer",
                        new XAttribute("ID", "B"),
                        new XAttribute("City", "Mumbai"),
                        new XAttribute("Region", "Asia"),
                        new XElement("order",
                            new XAttribute("Item", "Oven"),
                            new XAttribute("Price", )
                        )
                    )
                )
            );

            Console.WriteLine(xdoc2.ToString());

2.创建包含文本节点的Xml文档

            //使用字符串构建包含文本节点的XML文档
            XDocument xdocContent = new XDocument(
               new XElement("customers",
                   new XElement("customer",
                       new XAttribute("ID", "A"),
                       new XAttribute("City", "New York"),
                       new XAttribute("Region", "USA"),
                      "AAA"
                   ),
                   new XElement("customer",
                       new XAttribute("ID", "B"),
                       new XAttribute("City", "Mumbai"),
                       new XAttribute("Region", "Asia"),
                      "BBB"
                   )
               )
           );
            Console.WriteLine(xdocContent.ToString());

3.保存和加载Xml

从文件加载

            //使用Linq To XML 函数构建方式创建XML文档
            XDocument xdoc = new XDocument(
                new XElement("customers",
                    new XElement("customer",
                        new XAttribute("ID", "A"),
                        new XAttribute("City", "New York"),
                        new XAttribute("Region", "USA"),
                        new XElement("order",
                            new XAttribute("Item", "Widget"),
                            new XAttribute("Price", )
                        ),
                        new XElement("order",
                            new XAttribute("Item", "Tire"),
                            new XAttribute("Price", )
                        )
                    ),
                    new XElement("customer",
                        new XAttribute("ID", "B"),
                        new XAttribute("City", "Mumbai"),
                        new XAttribute("Region", "Asia"),
                        new XElement("order",
                            new XAttribute("Item", "Oven"),
                            new XAttribute("Price", )
                        )
                    )
                )
            );

            //从文件加载
            string fileName = "xmltest.xml";
            xdoc.Save(fileName);//保存生成的xml文档
            XDocument xdoc2 = XDocument.Load(fileName);//加载XML
            Console.WriteLine(xdoc2.ToString());

从字符串加载

            //注：ID=""A""使用双引号只是为了在@字符串中包含引号，也可以使用转义如ID=\"A\"
            string xmlContent = @"
                <customers>
                    <customer ID=""A"" City=""New York"" Region=""USA"">AAA</customer>
                    <customer ID=""B"" City=""Mumbai"" Region=""Asia"">BBB</customer>
                </customers>
                ";

            //使用Parse从字符串加载XML
            XDocument xdoc3 = XDocument.Parse(xmlContent);

4.处理Xml片段

处理Xml片段和处理Xml文档一样，只不过把Element当作顶级元素。xml片段可以应用到xml文档或者别的xml片段

            //处理XML片段
            XElement xcust = new XElement("customer",
                        new XAttribute("ID", "C"),
                        new XAttribute("City", "New York"),
                        new XAttribute("Region", "USA"),
                        new XElement("order",
                            new XAttribute("Item", "Widget"),
                            new XAttribute("Price", )
                        ),
                        new XElement("order",
                            new XAttribute("Item", "Tire"),
                            new XAttribute("Price", )
                        )
                    );
            string xcustFilePath = "xcust.xml";
            xcust.Save(xcustFilePath);

            XElement xcust2 = XElement.Load(xcustFilePath);
            xdoc.Root.Add(xcust2);//xml片段加到xml文档
            Console.WriteLine(xcust2);

 5.从数据库中生成XML

从数据库中生成XML先添加ADO.NET实体数据模型CustomerOrderEntities，然后利用添加的实体数据模型生成XML

            CustomerOrderEntities entity = new CustomerOrderEntities();
            XElement xdocSql = new XElement("Customers",
                from n in entity.tblCustomer.AsEnumerable()
                where n.Region != "Asia"
                select new XElement("Customer", new XAttribute("ID", n.ID),
                    new XAttribute("CustomerName", n.CustomerName),
                    from o in n.btlOrder
                    select new XElement("Order", new XAttribute("OrderId", o.OrderId),
                       new XAttribute("SKU", o.SKU),
                       new XAttribute("Qty", o.Qty)
                    )));
            Console.WriteLine(xdocSql.ToString());    

生成的XML如下

<Customers>
  <Customer ID="" CustomerName="tom">
    <Order OrderId="111-101" SKU="sku1" Qty="" />
    <Order OrderId="111-102" SKU="sku2" Qty="" />
  </Customer>
</Customers>

6.查询XML

//使用Linq To XML 函数构建方式创建XML文档
            XDocument xdoc = new XDocument(
                new XElement("customers",
                    new XElement("customer",
                        new XAttribute("ID", "A"),
                        new XAttribute("City", "New York"),
                        new XAttribute("Region", "USA"),
                        new XElement("order",
                            new XAttribute("Item", "Widget"),
                            new XAttribute("Price", )
                        ),
                        new XElement("order",
                            new XAttribute("Item", "Tire"),
                            new XAttribute("Price", )
                        )
                    ),
                    new XElement("customer",
                        new XAttribute("ID", "B"),
                        new XAttribute("City", "Mumbai"),
                        new XAttribute("Region", "Asia"),
                        new XElement("order",
                            new XAttribute("Item", "Oven"),
                            new XAttribute("Price", )
                        )
                    )
                )
            );
XElement queryResult = (from UserInfo in xdoc.Root.Elements("customer") where UserInfo.Attribute("ID").Value == "A" select UserInfo).SingleOrDefault();

返回的xml节点如下

<customer ID="A" City="New York" Region="USA">
  <order Item="Widget" Price="" />
  <order Item="Tire" Price="" />
</customer>

Elements()方法返回xml文档或者xml片段的所有一级元素，也可以传递节点名称返回该名称的所有一级元素

Descendants()返回所有级别的子元素，与之相反.Ancestors()返回当前节点以上的所有元素

Attributes()返回所有属性节点，Attributes("ID")返回所有属性为ID的属性节点，如 xdoc.Root.Elements("customer").Attributes("ID")返回元素节点customer的所有ID属性节点

Attribute("ID")返回ID属性节点