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Pro LINQ Language Integrated Query in C# 2010 ■ ■ ■ Adam Freeman and Joseph C. Rattz, Jr. ■ CONTENTS Pro LINQ: Language Integrated Query in C# 2010 Copyright © 2010 by Adam Freeman and Joseph C. Rattz, Jr. All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written permission of the copyright owner and the publisher. ISBN-13 (pbk): 978-1-4302-2653-6 ISBN-13 (electronic): 978-1-4302-2654-3 Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1 Trademarked names, logos, and images may appear in this book. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark. 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You will need to answer questions pertaining to this book in order to successfully download the code. ii ■ CONTENTS Dedicated to my wife, Jacqui Griffyth —Adam Freeman For my parents, Joe and Josie Rattz, that believed I could do anything and encouraged me to believe the same. Thank you. —Joseph C. Rattz, Jr. iii ■ CONTENTS Contents at a Glance Contents at a Glance ..........................................................................iv Contents ...........................................................................................vi About the Author............................................................................... xx About the Technical Reviewer ........................................................... xxi Acknowledgments........................................................................... xxii Part 1: Pro LINQ: Language Integrated Query in C# 2010.........................1 ■Chapter 1: Hello LINQ .......................................................................3 ■Chapter 2: C# Language Enhancements for LINQ ...............................21 Part 2: LINQ to Objects ......................................................................55 ■Chapter 3: LINQ to Objects Introduction............................................57 ■Chapter 4: Deferred Operators.........................................................69 ■Chapter 5: Nondeferred Operators.................................................. 151 Part 3: LINQ to XML......................................................................... 211 ■Chapter 6: LINQ to XML Introduction .............................................. 213 ■Chapter 7: The LINQ to XML API ..................................................... 219 ■Chapter 8: LINQ to XML Operators.................................................. 313 ■Chapter 9: Additional XML Capabilities........................................... 345 Part 4: LINQ to DataSet.................................................................... 387 ■Chapter 10: LINQ to DataSet Operators........................................... 389 ■Chapter 11: Additional DataSet Capabilities.................................... 427 Part 5: LINQ to SQL ...........................................................................55 ■Chapter 12: LINQ to SQL Introduction ............................................. 437 iv ■ CONTENTS ■Chapter 13: LINQ to SQL Tips and Tools.......................................... 449 ■Chapter 14: LINQ to SQL Database Operations................................. 475 ■Chapter 15: LINQ to SQL Entity Classes .......................................... 521 ■Chapter 16: The LINQ to SQL DataContext ....................................... 569 ■Chapter 17: LINQ to SQL Concurrency Conflicts............................... 635 ■Chapter 18: Additional LINQ to SQL Capabilities .............................. 653 Part 6: LINQ to Entities.................................................................... 665 ■Chapter 19: LINQ to Entities Introduction........................................ 667 ■Chapter 20: LINQ to Entities Operations.......................................... 679 ■Chapter 21: LINQ to Entities Classes .............................................. 723 Part 7: Parallel LINQ..........................................................................55 ■Chapter 22: Parallel LINQ Introduction ........................................... 751 ■Chapter 23: Using Parallel LINQ..................................................... 757 ■Chapter 24: Parallel LINQ Operators............................................... 773 Index ............................................................................................. 795 v ■ CONTENTS Contents Contents at a Glance ..........................................................................iv Contents ...........................................................................................vi About the Author............................................................................... xx About the Technical Reviewer ........................................................... xxi Acknowledgments........................................................................... xxii Part 1: Pro LINQ: Language Integrated Query in C# 2010.........................1 ■Chapter 1: Hello LINQ .......................................................................3 A Paradigm Shift.............................................................................................................3 Query XML.............................................................................................................................................4 Query a SQL Server Database................................................................................................................5 Introduction.....................................................................................................................7 LINQ Is About Data Queries....................................................................................................................7 How to Obtain LINQ................................................................................................................................8 LINQ Is Not Just for Queries............................................................................................8 Tips to Get You Started.................................................................................................12 Use the var Keyword When Confused..................................................................................................12 Use the Cast or OfType Operators for Legacy Collections.....................................................................................14 The OfType Operator versus the Cast Operator...................................................................................15 Don’t Assume a Query Is Bug-Free......................................................................................................15 Take Advantage of Deferred Queries...................................................................................................16 Use the DataContext Log.....................................................................................................................17 Use the LINQ Forum.............................................................................................................................18 Summary......................................................................................................................18 vi ■ CONTENTS ■Chapter 2: C# Language Enhancements for LINQ ...............................21 C# Language Additions.................................................................................................21 Lambda Expressions..............................................................................................................................................22 Expression Trees...................................................................................................................................................27 Keyword var, Object Initialization, and Anonymous Types....................................................................................28 Extension Methods................................................................................................................................................33 Partial Methods.....................................................................................................................................................39 Query Expressions.................................................................................................................................................41 Summary......................................................................................................................52 Part 2: LINQ to Objects ......................................................................55 ■Chapter 3: LINQ to Objects Introduction............................................57 LINQ to Objects Overview.............................................................................................57 IEnumerable<T>, Sequences, and the Standard Query Operators...............................58 Returning IEnumerable<T>, Yielding, and Deferred Queries.......................................59 Func Delegates.............................................................................................................62 The Standard Query Operators Alphabetical Cross-Reference.....................................64 A Tale of Two Syntaxes.................................................................................................66 Summary......................................................................................................................66 ■Chapter 4: Deferred Operators.........................................................69 Referenced Namespaces..............................................................................................69 Referenced Assemblies................................................................................................69 Common Classes..........................................................................................................69 The Deferred Operators by Purpose.............................................................................71 Restriction...........................................................................................................................................71 Projection.............................................................................................................................................74 Partitioning..........................................................................................................................................85 Concatenation........................................................................................................................................................93 Ordering.................................................................................................................................................................96 Join......................................................................................................................................................................116 vii ■ CONTENTS Grouping..............................................................................................................................................................120 Set.......................................................................................................................................................................126 Conversion.........................................................................................................................................133 Element..............................................................................................................................................140 Generation.........................................................................................................................................145 Summary....................................................................................................................148 ■Chapter 5: Nondeferred Operators.................................................. 151 Referenced Namespaces............................................................................................151 Common Classes........................................................................................................151 The Nondeferred Operators by Purpose.....................................................................154 Conversion...........................................................................................................................................................155 Equality................................................................................................................................................................168 Element................................................................................................................................................................172 Quantifiers...........................................................................................................................................................187 Aggregate............................................................................................................................................................193 Summary....................................................................................................................209 Part 3: LINQ to XML......................................................................... 211 ■Chapter 6: LINQ to XML Introduction .............................................. 213 Introduction.................................................................................................................215 Cheating the W3C DOM XML API.................................................................................216 Summary....................................................................................................................217 ■Chapter 7: The LINQ to XML API ..................................................... 219 Referenced Namespaces............................................................................................219 Significant API Design Enhancements........................................................................219 XML Tree Construction Simplified with Functional Construction......................................................220 Document Centricity Eliminated in Favor of Element Centricity........................................................222 Names, Namespaces, and Prefixes...................................................................................................224 Node Value Extraction.......................................................................................................................227 The LINQ to XML Object Model...................................................................................230 viii ■ CONTENTS Deferred Query Execution, Node Removal, and the Halloween Problem....................231 XML Creation..............................................................................................................234 Creating Elements with XElement.....................................................................................................234 Creating Attributes with XAttribute....................................................................................................237 Creating Comments with XComment.................................................................................................238 Creating Containers with XContainer.................................................................................................238 Creating Declarations with XDeclaration...........................................................................................239 Creating Document Types with XDocumentType...............................................................................240 Creating Documents with XDocument.................................................................................................................241 Creating Names with XName.............................................................................................................242 Creating Namespaces with XNamespace..........................................................................................243 Creating Nodes with XNode.................................................................................................................................243 Creating Processing Instructions with XProcessingInstruction.........................................................243 Creating Streaming Elements with XStreamingElement...................................................................246 Creating Text with XText....................................................................................................................247 Creating CData with XCData................................................................................................................................248 XML Output.................................................................................................................248 Saving with XDocument.Save()..........................................................................................................248 Saving with XElement.Save()...............................................................................................................................250 XML Input....................................................................................................................251 Loading with XDocument.Load()........................................................................................................251 Loading with XElement.Load()...........................................................................................................253 Parsing with XDocument.Parse() or XElement.Parse()......................................................................254 XML Traversal.............................................................................................................254 Traversal Properties..........................................................................................................................255 Traversal Methods.............................................................................................................................260 XML Modification........................................................................................................276 Adding Nodes......................................................................................................................................................276 Deleting Nodes..................................................................................................................................281 Updating Nodes.................................................................................................................................284 ix ■ CONTENTS XElement.SetElementValue() on Child XElement Objects..................................................................289 XML Attributes............................................................................................................290 Attribute Creation................................................................................................................................................291 Attribute Traversal.............................................................................................................................291 Attribute Modification........................................................................................................................295 XML Annotations.........................................................................................................300 Adding Annotations with XObject.AddAnnotation()............................................................................300 Accessing Annotations with XObject.Annotation() or XObject.Annotations().......................................................300 Removing Annotations with XObject.RemoveAnnotations()................................................................................301 Annotations Example...........................................................................................................................................301 XML Events.................................................................................................................304 XObject.Changing..............................................................................................................................305 XObject.Changed...............................................................................................................................305 A Couple of Event Examples..............................................................................................................306 Trick or Treat, or Undefined?.............................................................................................................310 Summary....................................................................................................................310 ■Chapter 8: LINQ to XML Operators.................................................. 313 Introduction to LINQ to XML Operators.......................................................................313 Ancestors....................................................................................................................314 Prototypes............................................................................................................................................................314 Examples...........................................................................................................................................314 AncestorsAndSelf.......................................................................................................319 Prototypes............................................................................................................................................................319 Examples...........................................................................................................................................319 Attributes....................................................................................................................322 Prototypes............................................................................................................................................................322 Examples...........................................................................................................................................322 DescendantNodes.......................................................................................................324 Prototypes............................................................................................................................................................324 Examples...........................................................................................................................................325 x