LINQ Pocket Reference

Projecting

Method	Description	SQL equivalents
Select	Transforms each input element with the given lambda expression	SELECT
SelectMany	Transforms each input element, then flattens and concatenates the resultant subsequences	INNER JOIN, LEFT OUTER JOIN, CROSS JOIN

Note

For LINQ to SQL queries, Select and SelectMany are the most versatile joining constructs; for local queries, Join and GroupJoin are the most efficient joining constructs.

Select

Argument	Type
Source sequence	IEnumerable<TSource>
Result selector	TSource => TResult or (TSource,int) => TResult [a]
[a] Prohibited with LINQ to SQL

*Comprehension syntax

	select projection-expression

Overview

With Select, you always get the same number of elements that you started with. Each element, however, can be transformed in any manner by the lambda function.

The following selects the names of all fonts installed on the computer (from System.Drawing):

	IEnumerable<string> query =
	  from f in FontFamily.Families
	  select f.Name;

	foreach (string name in query) Console.WriteLine (name);

In this example, the select clause converts a FontFamily object to its name. Here’s the lambda equivalent:

	IEnumerable<string> query =
	  FontFamily.Families.Select (f => f.Name);

Select statements are often used to project into anonymous types:

	var query =
	  from f in FontFamily.Families
	  select new
	  {
	    f.Name,
	    LineSpacing = f.GetLineSpacing (FontStyle.Bold)
	};

A projection with no transformation is sometimes used in comprehension queries to satisfy the requirement that the query ...