LINQ Pocket Reference

Filtering

Method	Description	SQL equivalents
Where	Returns a subset of elements that satisfy a given condition	WHERE
Take	Returns the first count elements, and discards the rest	WHERE ROW_NUMBER( )…orTOPn subquery
Skip	Ignores the first count elements, and returns the rest	WHERE ROW_NUMBER( )… or NOT IN (SELECT TOP n …)
TakeWhile	Emits elements from the input sequence until the predicate is true	Exception thrown
SkipWhile	Ignores elements from the input sequence until the predicate is true, and then emits the rest	Exception thrown
Distinct	Returns a collection that excludes duplicates	SELECT DISTINCT…

Note

The “SQL equivalents” column in the reference tables does not necessarily correspond to what an IQueryable implementation such as LINQ to SQL will produce. Rather, it indicates what you’d typically use to do the same job if you were writing the SQL query yourself. Where there is no simple translation, the column is left blank. Where there is no translation at all, the column reads “Exception thrown.”

Enumerable implementation code, when shown, excludes checking for null arguments, and indexing predicates.

With each of the filtering methods, you always end up with either the same number or fewer elements than you started with. You can never get more! The elements are also identical when they come out; they are not transformed in any way.

Where

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

Comprehension ...