C# LINQ Introduction

Projections with Select

With LINQ, you also can transform data from one representation into another.

The Select(transformationFunction) method allows you to project each element of a sequence into a new form. The method takes a transformation function as argument.

Here is a simple example. From a collection of numbers, calculate the square number of each element.

var numbers = new [] { 1, 2, 3, 4, 5 };
var squares = numbers.Select(x => x * x);   // 1, 4, 9, 16, 25

In the example above, the transformation function x => x * x is called for evrey element of numbers. This projects the sequence of integers (numbers) to a new sequence of integers (squares).

But with Select you can also transform the type of a sequence.

Here is another example. From a collection of person objects, select only the names.

The example above projects the IEnumerable<Person> to an IEnumerable<string>.