Language Integrated Query (LINQ), as well as the C# 3.0 and VB 9.0 language extensions to support it, is the most import single new feature of Visual Studio 2008 and the .NET Framework 3.x. LINQ is Microsoft’s first attempt to define a universal query language for a diverse set of in-memory collections of generic objects, entities persisted in relational database tables, and element and attributes of XML documents or fragments, as well as a wide variety of other data types, such as RSS and Atom syndication feeds. Microsoft invested millions of dollars in Anders Hejlsberg and his C# design and development groups to add new features to C# 3.0—such as lambda expressions, anonymous types, and extension methods—specifically to support LINQ Standard Query Operators (SQOs) and query expressions as a part of the language itself.
Corresponding additions to VB 9.0 followed the C# team’s lead, but VB’s implementation of LINQ to XML offers a remarkable new addition to the language: XML literals. VB’s LINQ to XML implementation includes XML literals, which treat well-formed XML documents or fragments as part of the VB language, rather than requiring translation of element and attribute names and values from strings to XML DOM nodes and values.
This book concentrates on hands-on development of practical Windows and Web applications that demonstrate C# and VB programming techniques to bring you up to speed on LINQ technologies. The first half of the book covers LINQ Standard Query Operators (SQOs) and the concrete implementations of LINQ for querying collections that implement generic IEnumerable<T>, IQueryable<T>, or both interfaces. The second half is devoted to the ADO.NET Entity Framework, Entity Data Model, Entity SQL (eSQL) and LINQ to Entities. Most code examples emulate real-world data sources, such as the Northwind sample database running on SQL Server 2005 or 2008 Express Edition, and collections derived from its tables. Code examples are C# and VB Windows form or Web site/application projects not, except in the first chapter, simple command-line projects. You can’t gain a feel for the behavior or performance of LINQ queries with “Hello World” projects that process arrays of a few integers or a few first and last names.
This book is intended for experienced .NET developers using C# or VB who want to gain the maximum advantage from the query-processing capabilities of LINQ implementations in Visual Studio 2008—LINQ to Objects, LINQ to SQL, LINQ to DataSets, and LINQ to XML—as well as the object/relational mapping (O/RM) features of VS 2008 SP1’s Entity Framework/Entity Data Model and LINQ to Entities and the increasing number of open-source LINQ implementations by third-party developers.
Basic familiarity with generics and other language features introduced by .NET 2.0, the Visual Studio integrated development environment (IDE), and relational database management systems (RDBMSs), especially Microsoft SQL Server 200x, is assumed. Experience with SQL Server’s Transact-SQL (T-SQL) query language and stored procedures will be helpful but is not required. Proficiency with VS 2005, .NET 2.0, C# 2.0, or VB 8.0 will aid your initial understanding of the book’s C# 3.0 or VB 9.0 code samples but isn’t a prerequisite.
