LINQ to XML 进阶篇(四)

 ////编写使用复杂筛选的查询
            XElement root = XElement.Load("PurchaseOrders.xml");
            IEnumerable<XElement> purchaseOrders =
                from el in root.Elements("PurchaseOrder")
                where
                    (from add in el.Elements("Address")
                     where
                         (string)add.Attribute("Type") == "Shipping" &&
                         (string)add.Element("State") == "NY"
                     select add)
                    .Any()
                select el;
            foreach (XElement el in purchaseOrders)
                Console.WriteLine((string)el.Attribute("PurchaseOrderNumber"));

            //            //筛选可选元素
            XElement root = XElement.Parse(@"<Root>
                          <Child1>
                            <Text>Child One Text</Text>
                            <Type Value=""Yes""/>
                          </Child1>
                          <Child2>
                            <Text>Child Two Text</Text>
                            <Type Value=""Yes""/>
                          </Child2>
                          <Child3>
                            <Text>Child Three Text</Text>
                            <Type Value=""No""/>
                          </Child3>
                          <Child4>
                            <Text>Child Four Text</Text>
                            <Type Value=""Yes""/>
                          </Child4>
                          <Child5>
                            <Text>Child Five Text</Text>
                          </Child5>
                        </Root>");
            var cList =
                from typeElement in root.Elements().Elements("Type")
                where (string)typeElement.Attribute("Value") == "Yes"
                select (string)typeElement.Parent.Element("Text");
            foreach (string str in cList)
                Console.WriteLine(str);

//对元素进行排序
            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);

 ////对多个键上的元素进行排序
            XElement co = XElement.Load("CustomersOrders.xml");
            var sortedElements =
                from c in co.Element("Orders").Elements("Order")
                orderby (string)c.Element("ShipInfo").Element("ShipPostalCode"),
                        (DateTime)c.Element("OrderDate")
                select new
                {
                    CustomerID = (string)c.Element("CustomerID"),
                    EmployeeID = (string)c.Element("EmployeeID"),
                    ShipPostalCode = (string)c.Element("ShipInfo").Element("ShipPostalCode"),
                    OrderDate = (DateTime)c.Element("OrderDate")
                };
            foreach (var r in sortedElements)
                Console.WriteLine("CustomerID:{0} EmployeeID:{1} ShipPostalCode:{2} OrderDate:{3:d}",
                    r.CustomerID, r.EmployeeID, r.ShipPostalCode, r.OrderDate);

 

 ////计算中间值
            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);

 

 //编写基于上下文查找元素的查询
            XElement doc = XElement.Parse(@"<Root>
                            <p id=""1""/>
                            <ul>abc</ul>
                            <Child>
                                <p id=""2""/>
                                <notul/>
                                <p id=""3""/>
                                <ul>def</ul>
                                <p id=""4""/>
                            </Child>
                            <Child>
                                <p id=""5""/>
                                <notul/>
                                <p id=""6""/>
                                <ul>abc</ul>
                                <p id=""7""/>
                            </Child>
                        </Root>");

            IEnumerable<XElement> items =
                from e in doc.Descendants("p")
                let z = e.ElementsAfterSelf().FirstOrDefault()
                where z != null && z.Name.LocalName == "ul"
                select e;

            foreach (XElement e in items)
                Console.WriteLine("id = {0}", (string)e.Attribute("id"));

 

////通过 LINQ to XML 使用字典
            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)
            );

  Dictionary<string, string> dict = new Dictionary<string, string>();
            foreach (XElement el in root.Elements())
                dict.Add(el.Name.LocalName, el.Value);
            foreach (string str in dict.Keys)
                Console.WriteLine("{0}:{1}", str, dict[str]);
            Console.WriteLine(root);