LINQ to XML provides an in-memory XML programming interface that leverages LINQ. It uses .NET language capabilities to provide strongly typed access to XML elements and attributes. The document discusses LINQ to XML classes like XDocument and XElement, and provides code samples to query an XML document to retrieve purchase orders over $40, orders with at least 2 items, and how to query a repeating table in an InfoPath form.

1. Monthly Features: Technical ShowcaseWhat is LINQ to XML?Microsoft says:“LINQ to XML provides an in-memory XML programming interface that leverages the .NET Language-Integrated Query (LINQ) Framework. LINQ to XML uses the latest .NET Framework language capabilities and is comparable to an updated, redesigned Document Object Model (DOM) XML programming interface.”

2. Monthly Features: Technical ShowcaseWhat is LINQ to XML?Alternative to using XPathUses anonymous types to provide strongly typed access to XML elements and attributes.Not a replacement for XSLT

3. Monthly Features: Technical ShowcaseSample XML File<?xmlversion="1.0"encoding="utf-8" ?><PurchaseOrders> <PurchaseOrderId="83123"Total="59.97"> <CustomerName>Joe Bob</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="32324"Name="T-Shirt"Color="White"Price="9.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83124"Total="19.99"> <CustomerName>Bob Joe</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Red"Price="19.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83125"Total="49.98"> <CustomerName>John Smith</CustomerName> <CustomerState>OK</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder></PurchaseOrders>

4. Monthly Features: Technical ShowcaseGet PurchaseIds of orders greater than $40.00ReturnsXDocumentpurchaseOrderXml = XDocument.Load("PurchaseOrder.xml"); varpurchaseIds = frompurchaseOrderinpurchaseOrderXml.Root.Elements("PurchaseOrder") wherefloat.Parse(purchaseOrder.Attribute("Total").Value) > 40.00f selectpurchaseOrder.Attribute("Id").Value; foreach (varpurchaseIdinpurchaseIds) Console.WriteLine("PurchaseId: {0}", purchaseId);Order Ids Greater than $40.00PurchaseId: 83123PurchaseId: 83125

5. Monthly Features: Technical ShowcaseAdd a reference to System.Xml.Linq.ClassesXDocument– Class used to interact with an XML documentXElement– Represents an element in an XML documentXAttribute– Represents an attribute in an XML documentXNamespace – Used to specify a namespace in an XML document i.e.: /my:myFields/my:RepeatingTableLINQ to XML Classes

6. Monthly Features: Technical ShowcaseMethods and PropertiesXDocument.Root– Returns the root XElement of the XML documentXContainer.Elements() – Returns an IEnumberable<XElement> of all matching elements Example: myDocument.Root.Elements(“PurchaseOrders”);XContainer.Attributes() – Returns an IEnumerable<XAttribute>XContainer.Element() – Returns a single XElementExample: purchaseOrderElement.Element(“CustomerName”).Value;XContainer.Attribute() – Returns a single XAttribute.Any() Extension Method – Returns true if items exist in a IEnumerable<>.First() Extension Method – Returns first item in an IEnumberable<>LINQ to XML Methods and Properties

7. Monthly Features: Technical ShowcaseSample XML File<?xmlversion="1.0"encoding="utf-8" ?><PurchaseOrders> <PurchaseOrderId="83123"Total="59.97"> <CustomerName>Joe Bob</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="32324"Name="T-Shirt"Color="White"Price="9.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83124"Total="19.99"> <CustomerName>Bob Joe</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Red"Price="19.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83125"Total="49.98"> <CustomerName>John Smith</CustomerName> <CustomerState>OK</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder></PurchaseOrders>

8. Monthly Features: Technical ShowcaseGet Purchase Orders greater than $40.00ReturnsXDocumentpurchaseOrderXml = XDocument.Load("PurchaseOrder.xml"); varpurchaseOrders = frompurchaseOrderinpurchaseOrderXml.Root.Elements("PurchaseOrder") wherefloat.Parse(purchaseOrder.Attribute("Total").Value) > 40.00f selectnew { Id = purchaseOrder.Attribute("Id").Value, Total = float.Parse(purchaseOrder.Attribute("Total").Value), CustomerName = purchaseOrder.Element("CustomerName").Value, CustomerState = purchaseOrder.Element("CustomerState").Value }; foreach (varpurchaseOrderinpurchaseOrders) Console.WriteLine("PurchaseId: {0}: {1} ({2}) - {3}", purchaseOrder.Id, purchaseOrder.CustomerName, purchaseOrder.CustomerState, purchaseOrder.Total);ReturnsOrders Greater than $40.00PurchaseId: 83123: Joe Bob (TX) - 59.97PurchaseId: 83125: John Smith (OK) - 49.98

9. Monthly Features: Technical ShowcaseSample XML File<?xmlversion="1.0"encoding="utf-8" ?><PurchaseOrders> <PurchaseOrderId="83123"Total="59.97"> <CustomerName>Joe Bob</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="32324"Name="T-Shirt"Color="White"Price="9.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83124"Total="19.99"> <CustomerName>Bob Joe</CustomerName> <CustomerState>TX</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Red"Price="19.99" /> </Items> </PurchaseOrder> <PurchaseOrderId="83125"Total="49.98"> <CustomerName>John Smith</CustomerName> <CustomerState>OK</CustomerState> <Items> <ItemId="26134"Name="Polo Shirt"Color="Blue"Price="19.99" /> <ItemId="01283"Name="Jeans"Color="Blue"Price="29.99" /> </Items> </PurchaseOrder></PurchaseOrders>

10. Monthly Features: Technical ShowcaseGet Purchase Orders with at least 2 itemsReturnsXDocumentpurchaseOrderXml = XDocument.Load("PurchaseOrder.xml"); varpurchaseOrders = frompurchaseOrderinpurchaseOrderXml.Root.Elements("PurchaseOrder") wherepurchaseOrder.Element("Items").Elements("Item").Count() >= 2 selectnew { Id = purchaseOrder.Attribute("Id").Value, ItemCount = purchaseOrder.Element("Items").Elements("Item").Count() }; foreach (varpurchaseOrderinpurchaseOrders) Console.WriteLine("PurchaseId: {0}: ItemCount: {1}", purchaseOrder.Id, purchaseOrder.ItemCount);ReturnsOrders With at least 2 itemsPurchaseId: 83123: ItemCount: 3PurchaseId: 83125: ItemCount: 2

11. Monthly Features: Technical ShowcaseInfoPath<my:myFieldsxmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:my="http://schemas.microsoft.com/office/infopath/2003/myXSD/2008-12-30T15:48:37" xmlns:xd="http://schemas.microsoft.com/office/infopath/2003"xml:lang="en-US"> <my:RepeatingTable> <my:Item> <my:Name>Polo Shirt</my:Name> <my:Color>Red</my:Color> <my:Price>19.99</my:Price> </my:Item> <my:Item> <my:Name>Jeans</my:Name> <my:Color>Blue</my:Color> <my:Price>29.99</my:Price> </my:Item> </my:RepeatingTable> <my:Id>83123</my:Id></my:myFields>

12. Monthly Features: Technical ShowcaseQuerying a repeating table in InfoPathReference System.Linq (contained in System.Core)Reference System.Xml.Linq (contained in System.Xml.Linq)Returns// use the MainDataSource to read the XML of the InfoPath FormXDocumentinfoPathDocument = XDocument.Load(newSystem.IO.StringReader(MainDataSource.CreateNavigator().OuterXml)); // required to access my: namespaceXNamespacemyNamespace = "http://schemas.microsoft.com/office/infopath/2003/myXSD/2008-12-30T15:48:37"; // use descendants node to find any element with the name Item in the treevar items = from item ininfoPathDocument.Descendants(myNamespace + "Item") selectnew { Name = item.Element(myNamespace + "Name").Value, Color = item.Element(myNamespace + “Color").Value, Price = item.Element(myNamespace + "Price").Value }; foreach (var item in items){ // do something}

13. Monthly Features: Technical ShowcaseQuestions?Code Samples available at www.dotnetmafia.com.