C# Learning: LINQ as a toolset

LINQ offers numerous possibilities. It will significantly change some aspects of how
you handle and manipulate data with your applications and components.

There are three major flavors of LINQ, or LINQ provider s : LINQ to Objects, LINQ to SQL, and LINQ to XML.

e.g.

database access:
var contacts =
from customer in db.Customers
where customer.Name.StartsWith("A") && customer.Orders.Count > 0
orderby customer.Name
select new { customer.Name, customer.Phone };

xml query:
var xml =
new XElement("contacts",
from contact in contacts
select new XElement("contact",
new XAttribute("name", contact.Name),
new XAttribute("phone", contact.Phone)
)
);


The main idea is that by using LINQ you are able to gain access to any data
source by writing queries like the one shown in listing below, directly in the programming
language that you master and use every day.

from customer in customers
where customer.Name.StartsWith("A") && customer.Orders.Count > 0
orderby customer.Name
select new { customer.Name, customer.Orders }

In this query, the data could be in memory, in a database, in an XML document,
or in another place; the syntax would remain similar if not exactly the same. This kind of query can be used with multiple types of data and different data sources, thanks to LINQ’s extensibility features. For example, in
the future we are likely to see an implementation of LINQ for querying a file system or for calling web services.