C# 0 The Complete Reference

select

.)

The

group

 clause has the following general form:

group 

range-variable

 by 

key

It returns data grouped into sequences, with each sequence sharing the key specified by 

key

.

The result of 

group

 is a sequence that contains elements of type 

IGrouping

TElement>

, which is declared in the 

System.Linq

 namespace. It defines a collection of 

objects that share a common key. The type of query variable in a query that returns a group 

is

IEnumerable>

.

IGrouping

 defines a read-only property 

called

Key

, which returns the key associated with each sequence.

Here is an example that illustrates the use of 

group

. It declares an array that contains a 

list of websites. It then creates a query that groups the list by top-level domain name, such 

as