XML LINQing in the Real World

with Paul D. Sheriff

What is LINQ to XML

• LINQ to XML was developed with Language-Integrated Query over XML in mind and takes advantage of standard query operators and adds query extensions specific to XML
• Found in System. XML. LINQ NameSpace and adds
• XDocument type
• XElement type
• If you want to use XPath elements you need to add the NameSpace as the are extension methods
• LINQ provides compile time exceptions where you’d rely on runtime exceptions before

VB.Net versus C#

• VB.Net does a better job on the LINQ to XML stuff
• VB.Net has XML literals
• as long as you have an XSD file with your xml file, you'll get intellisense

Uses

• useful for Rapid Application Development and prototyping
• You can do CRUD of XML with LINQ too
• Allows for easy creation of XML from scratch in code
• use this for unit testing perhaps
• LINQ allows you to aggregate data as well
• VB.Net has an Aggregate/Into syntax as well. Probably not the best approach.
• You can insert script blocks into inline SQL to create xml data that contains dynamic data <%=something%>
• This is useful for creating xml documents from data in a database

Anonymous types

• These are on the fly classes
• Scoped within the block of code in which it is defined
• You can return anonymous types, but you get no intellisense
• These do not work with updates

EFPRS

• The translat can be rewritten (again) to use this approach to make it more maintainable

Notes

• Remember XML is case sensitive
• In LINQ “from” comes first and “select” comes last
• for intellisense reasons
• Sample code and a free ebook!