LINQ Pocket Reference

Ordering

Method	Description	SQL equivalents
OrderBy, ThenBy	Sorts a sequence in ascending order	ORDER BY …
OrderByDescending, ThenByDescending	Sorts a sequence in descending order	ORDER BY …DESC
Reverse	Returns a sequence in reverse order	Exception thrown

Ordering operators return the same elements in a different order.

OrderBy, OrderByDescending, ThenBy, ThenByDescending

OrderBy, OrderByDescending arguments

Argument	Type
Input sequence	IEnumerable<TSource>
Key selector	TSource => Tkey

Return type = IOrderedEnumerable<TSource>

ThenBy, ThenByDescending arguments

Argument	Type
Input sequence	IOrderedEnumerable<TSource>
Key selector	TSource => Tkey

Comprehension syntax

orderby expression1 [descending]
	  [, expression2 [descending] ... ]

Overview

OrderBy returns a sorted version of the input sequence, using the keySelector expression to make comparisons. The following query emits a sequence of names in alphabetical order:

	IEnumerable<string> query = names.OrderBy (s=> s);

The following sorts names by length:

	IEnumerable<string> query =
	  names.OrderBy (s => s.Length);

	// Result: { "Jay", "Tom", "Mary", "Dick", "Harry" };

The relative order of elements with the same sorting key (in this case, Jay/Tom and Mary/Dick) is indeterminate—unless you append a ThenBy operator:

	IEnumerable<string> query = names.OrderBy (s => s.Length)
	                                       . ThenBy (s => s);

	// Result: { "Jay", "Tom", "Dick", "Mary", "Harry" };

ThenBy reorders only elements that had the same sorting key in the preceding sort. You can chain any number of ...