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Note

Chapter 24 will examine additional LINQ-centric APIs that allow you to interact with relational databases

and XML documents.

Understanding the Role of LINQ

As software developers, it is hard to deny that the vast majority of our programming time is spent

obtaining and manipulating 

data. When speaking of “data,” it is very easy to immediately envision

information contained within relational databases. However, another popular location in which

data exists is within XML documents (*.config files, locally persisted DataSets, in-memory data

returned from XML web services, etc.).

Data can be found in numerous places beyond these two common homes for information. For

instance, say you have a generic List type containing 300 integers, and you want to obtain a

subset that meets a given criterion (e.g., only the odd or even members in the container, only prime

numbers, only nonrepeating numbers greater than 50, etc.). Or perhaps you are making use of the

reflection APIs and need to obtain only metadata descriptions for each class deriving from a partic-

ular parent class within an array of Types. Indeed, data is everywhere.

Prior to .NET 3.5, interacting with a particular flavor of data required programmers to make use

of diverse APIs. Consider, for example, Table 14-1, which illustrates several common APIs used to

access various types of data.

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Table 14-1.

Ways to Manipulate Various Types of Data