Chapter 14. Language Integrated Query (LINQ)

One of the most exciting new features in the .NET Framework v3.5 is the Language Integrated Query (LINQ). LINQ introduces to developers a standard and consistent language for querying and updating data, which include objects (such as arrays and collections), databases, XML documents, ADO.NET DataSets, and so forth.

Today, most developers need to know a myriad of technologies to successfully manipulate data. For example, if you are dealing with databases, you have to understand Structured Query Language (SQL). If you are dealing with XML documents, you must understand technologies such as XPath, XQuery, and XSLT. And if you are working with ADO.NET DataSets, then you need to know the various classes and properties in ADO.NET that you can use.

A better approach would be to have a unified view of the data, regardless of its form and structure. That is the motivation behind the design of LINQ. This chapter provides the basics of LINQ and shows how you can use LINQ to access objects, DataSets, and XML documents, as well as SQL databases.

LINQ Architecture

Figure 14-1 shows the architecture of LINQ. The bottom layer contains the various data sources with which your applications could be working. On top of the data sources are the LINQ-enabled data sources: LINQ to Objects, LINQ to DataSet, LINQ to SQL, LINQ to Entities, and LINQ to XML. LINQ-enabled data sources are also known as LINQ providers; they translate queries expressed in Visual Basic ...

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