System.Linq Namespace

The System.Linq namespace is in the System.Core assembly (in System.Core.dll).

The Enumerable class contains LINQ standard query operators that operate on objects that implement IEnumerable<T>.

The Queryable class contains LINQ standard query operators that operate on objects that implement IQueryable<T>.

For information about LINQ to SQL, see LINQ to SQL.

Classes

---

	Class	Description
	Enumerable	Provides a set of static (Shared in Visual Basic) methods for querying objects that implement IEnumerable<T>.
	EnumerableExecutor	Represents an expression tree and provides functionality to execute the expression tree after rewriting it.
	EnumerableExecutor<T>	Infrastructure. Represents an expression tree and provides functionality to execute the expression tree after rewriting it.
	EnumerableQuery	Infrastructure. Represents an IEnumerable as an EnumerableQuery data source.
	EnumerableQuery<T>	Infrastructure. Represents an IEnumerable<T> collection as an IQueryable<T> data source.
	Lookup<TKey, TElement>	Represents a collection of keys each mapped to one or more values.
	OrderedParallelQuery<TSource>	Represents a sorted, parallel sequence.
	ParallelEnumerable	Provides a set of methods for querying objects that implement ParallelQuery{TSource}. This is the parallel equivalent of Enumerable.
	ParallelQuery	Represents a parallel sequence.
	ParallelQuery<TSource>	Represents a parallel sequence.
	Queryable	Provides a set of static (Shared in Visual Basic) methods for querying data structures that implement IQueryable<T>.

Interfaces

---

	Interface	Description
	IGrouping<TKey, TElement>	Represents a collection of objects that have a common key.
	ILookup<TKey, TElement>	Defines an indexer, size property, and Boolean search method for data structures that map keys to IEnumerable<T> sequences of values.
	IOrderedEnumerable<TElement>	Represents a sorted sequence.
	IOrderedQueryable	Represents the result of a sorting operation.
	IOrderedQueryable<T>	Represents the result of a sorting operation.
	IQueryable	Provides functionality to evaluate queries against a specific data source wherein the type of the data is not specified.
	IQueryable<T>	Provides functionality to evaluate queries against a specific data source wherein the type of the data is known.
	IQueryProvider	Defines methods to create and execute queries that are described by an IQueryable object.

Enumerations

---

	Enumeration	Description
	ParallelExecutionMode	The query execution mode is a hint that specifies how the system should handle performance trade-offs when parallelizing queries.
	ParallelMergeOptions	Specifies the preferred type of output merge to use in a query. In other words, it indicates how PLINQ should merge the results from the various partitions back into a single result sequence. This is a hint only, and may not be respected by the system when parallelizing all queries.