Paolo Pialorsi & Marco Russo 
Programming Microsoft LINQ in .NET Framework 4 [PDF ebook] 

Dig into LINQ — and transform the way you work with data. With LINQ, you can query data from a variety of sources — including databases, objects, and XML files — directly from Microsoft Visual Basic or C#. Guided by data-access experts who’ve worked in depth with LINQ and the Microsoft development teams, you’ll learn how .NET Framework 4 implements LINQ, and how to exploit it. Clear examples show you how to deliver your own data-access solutions faster and with leaner code. Discover how to: Use LINQ to query databases, object collections, arrays, XML, Microsoft Excel files, and other sources Apply LINQ best practices to build data-enabled .NET applications and services Manipulate data in a relational database with ADO.NET Entity Framework or LINQ to SQL Read, write, and manage XML content more efficiently with LINQ to XML Extend LINQ to support additional data sources by creating custom operators and providers Examine other implementations, such as LINQ to Share Point Use LINQ within the data, business, and service layers of a distributed application Get code samples on the Web