Simplifying XML Processing using LINQ to XML

1. SESSION CODE: DEV320 Simplifying XML Processing using LINQ to XML By: Paul D. Sheriff PSheriff@pdsa.com www.pdsa.com or www.PaulSheriffInnerCircle.com

2. Paul.About • Paul D. Sheriff (psheriff@pdsa.com) • President of PDSA, Inc. • Custom Software Development, Developer Tools • www.pdsa.com • eBooks (www.pdsa.com/eBooks) • Several .NET, SQL Server and SharePoint Topics • Developer Tools • .NET Productivity Framework • Paul Sheriff's Inner Circle • www.PaulSheriffInnerCircle.com

3. Agenda • Using the System.Xml.Linq Namespace • What is LINQ • LINQ TO XML Basics • LINQ Query Syntax • Demonstrations • A Prototyping System

4. Goals of this Session • Show you how to use LINQ to XML • Use anonymous types • Load a class from XML • Add/Edit/Delete XML files

5. System.Xml.Linq Namespace • New classes for dealing with XML • XDocument • Represents a complete, valid XML document • XElement • Represents an XML element or elements • Both provide XPath query capabilities • XPathSelectElement • XPathSelectElements

6. Build XML in Code • New syntax=easy creation of XML • Implicit type declaration VB.NET Dim menu = _ New XDocument( _ New XDeclaration("1.0", "utf-8", "yes"), _ New XComment("Prototype Menus"), _ New XElement("Menus")) C# var menu = new XDocument( new XDeclaration("1.0", "utf-8", "yes"), new XComment("Prototype Menus"), new XElement("Menus"));

7. Build XML in Code (2) • Create full document VB.NET Dim menu = _ New XDocument( _ New XDeclaration("1.0", "utf-8", "yes"), _ New XComment("Prototype Menus"), _ New XElement("Menus", _ New XElement("Menu", _ New XElement("MenuID", "10"), _ New XElement("DisplayOrder", "10"), _ New XElement("MenuText", "Home") _ )))

8. VB.NET XML Literals • Only available in VB.NET VB.NET Dim menu = _ <Menus> <Menu> <MenuID>10</MenuID> <DisplayOrder>10</DisplayOrder> <MenuText>Home</MenuText> <Action>NextPage.aspx</Action> <ParentMenuID></ParentMenuID> </Menu> </Menus>

9. Loading a Document • XDocument.Load("Menus.xml") • Loads a complete valid XML Document • XElement.Load("Menus.xml") • Loads a set of XML Elements

10. Build XML / Load Document DEMO

11. LINQ to XML • Special LINQ syntax for dealing with XML • Simpler than using DOM • Comparable to using XPath and XQuery • Although syntax is much different • IntelliSense • In VB.NET only • When using XSD

12. LINQ Query Syntax • Standard “SQL-like” query syntax VB.NET From <element> in <collection> _ Where <condition> _ Order By <Expression> [Ascending | Descending] Select [<alias> = ] <column>, [<alias> = ] <column>… C# from <element> in <collection> where <condition> orderby <Expression> [ascending | descending] select <column>, <column>…

13. LINQ Query Syntax • Here is a sample VB.NET Dim menus = From mnu In xElem.<Menu> _ Where mnu.<ParentMenuID>.Value = "" _ Select mnu C# var menus = from mnu in xdoc.Descendants("Menu") where mnu.Element("ParentMenuID").Value == "" select mnu;

14. Select a Single Node • Method 1 • Load XML using XElement class • XElement.Load() • Use the XPathSelectElement method • Returns an XElement object • This is a LINQ Extension method • import/using System.Xml.XPath namespace • Method 2 • Use LINQ to XML Syntax

15. Select Single Node DEMO

16. Select Multiple Nodes • Method 1 • Use the XPathSelectElements method • LINQ Extension method • import/using System.Xml.XPath namespace • Can iterate using For Each / foreach • Method 2 • Use LINQ Query Syntax

17. Select Multiple Nodes DEMO

18. VB XML Script • VB Allows you to script in XML Literals Dim db As New NorthwindDataContext Dim products = <Products> <%= From prod In db.Products _ Select <Product> <ProductName><%= prod.ProductName%> </ProductName> <UnitPrice><%= prod.UnitPrice %> </UnitPrice> </Product> %> </Products>

19. VB XML Script DEMO

20. Anonymous Types • Create your own custom type • Define new field names • Compiler creates new type • Sort of like an on-the-fly class • Each field is assigned a data type based on return value • You get IntelliSense on these new names

21. Anonymous Types DEMO

22. Aggregating Data • LINQ allows you to aggregate data • Sum, Min, Max, Avg, etc. • Instead of you having to loop through all the data, LINQ does it for you

23. Aggregating Data DEMO

24. Adding using LINQ • Method 1: VB.NET Only • Use XML Literal • Method 2 • Create XElement object, Populate Data • Save XML using XElement.Save method • Method 3 • Select an XElement using LINQ • Clone Element • Save XML using XElement.Save method

25. Updating using LINQ • Method 1 • Select element to update • XPathSelectElement • Update element • Save XML using XElement.Save method • Method 2 • Select using LINQ • Update elements • Save XML using XElement.Save method

26. Deleting using LINQ • Method 1 • Select element to delete • XPathSelectElement • Use the Remove method on the XElement • Save XML using XElement.Save method • Method 2 • Select using LINQ • Remove the Element • Save XML using XElement.Save method

27. Add/Edit/Delete using LINQ DEMO

28. A Prototype Application • Problem: • Want to quickly prototype application • Don’t want to setup a database • Would be nice to use XML for menu system • Solution • Create a standard prototype application • Use LINQ to XML for all menuing • Can be used on Compact Framework • LINQ to XML works (LINQ to SQL does not)

29. A Prototype Application DEMO

30. A Wrapper Class • If you want, you could wrap all these calls • Create class to do all LINQ to XML • Just use the class from the UI • Later change the class to go to database

31. A Wrapper Class DEMO

32. Summary • LINQ to XML makes processing XML easy • Full add/edit/delete • Nice Select syntax • Should simplify a lot of XML processing

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