System.Collections.Generic Namespace

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Contains interfaces and classes that define generic collections, which allow users to create strongly typed collections that provide better type safety and performance than non-generic strongly typed collections.

Classes

Name	Description
CollectionExtensions	Provides extension methods for generic collections.
Comparer	Provides a base class for implementations of the IComparer generic interface.
Dictionary.KeyCollection	Represents the collection of keys in a Dictionary. This class cannot be inherited.
Dictionary.ValueCollection	Represents the collection of values in a Dictionary. This class cannot be inherited.
Dictionary	Represents a collection of keys and values.
EqualityComparer	Provides a base class for implementations of the IEqualityComparer generic interface.
HashSet	Represents a set of values.
KeyedByTypeCollection	Provides a collection whose items are types that serve as keys.
KeyNotFoundException	The exception that is thrown when the key specified for accessing an element in a collection does not match any key in the collection.
KeyValuePair	Creates instances of the KeyValuePair struct.
LinkedList	Represents a doubly linked list.
LinkedListNode	Represents a node in a LinkedList. This class cannot be inherited.
List	Represents a strongly typed list of objects that can be accessed by index. Provides methods to search, sort, and manipulate lists.
OrderedDictionary.KeyCollection	Represents the collection of keys in a OrderedDictionary.
OrderedDictionary.ValueCollection	Represents the collection of values in a OrderedDictionary.
OrderedDictionary	Represents a collection of key/value pairs that are accessible by the key or index.
PriorityQueue.UnorderedItemsCollection	Enumerates the contents of a PriorityQueue, without any ordering guarantees.
PriorityQueue	Represents a collection of items that have a value and a priority. On dequeue, the item with the lowest priority value is removed.
Queue	Represents a first-in, first-out collection of objects.
ReferenceEqualityComparer	An IEqualityComparer that uses reference equality (ReferenceEquals(Object, Object)) instead of value equality (Equals(Object)) when comparing two object instances.
SortedDictionary.KeyCollection	Represents the collection of keys in a SortedDictionary. This class cannot be inherited.
SortedDictionary.ValueCollection	Represents the collection of values in a SortedDictionary. This class cannot be inherited.
SortedDictionary	Represents a collection of key/value pairs that are sorted on the key.
SortedList	Represents a collection of key/value pairs that are sorted by key based on the associated IComparer implementation.
SortedSet	Represents a collection of objects that is maintained in sorted order.
Stack	Represents a variable size last-in-first-out (LIFO) collection of instances of the same specified type.
SynchronizedCollection	Provides a thread-safe collection that contains objects of a type specified by the generic parameter as elements.
SynchronizedKeyedCollection	Provides a thread-safe collection that contains objects of a type specified by a generic parameter and that are grouped by keys.
SynchronizedReadOnlyCollection	Provides a thread-safe, read-only collection that contains objects of a type specified by the generic parameter as elements.

Structs

Name	Description
Dictionary.AlternateLookup	Provides a type that can be used to perform operations on a Dictionary using a `TAlternateKey` as a key instead of a `TKey`.
Dictionary.Enumerator	Enumerates the elements of a Dictionary.
Dictionary.KeyCollection.Enumerator	Enumerates the elements of a Dictionary.KeyCollection.
Dictionary.ValueCollection.Enumerator	Enumerates the elements of a Dictionary.ValueCollection.
HashSet.AlternateLookup	Provides a type that can be used to perform operations on a HashSet using a `TAlternate` instead of a `T`.
HashSet.Enumerator	Enumerates the elements of a HashSet object.
KeyValuePair	Defines a key/value pair that can be set or retrieved.
LinkedList.Enumerator	Enumerates the elements of a LinkedList.
List.Enumerator	Enumerates the elements of a List.
OrderedDictionary.Enumerator	Enumerates the elements of a OrderedDictionary.
OrderedDictionary.KeyCollection.Enumerator	Enumerates the elements of a OrderedDictionary.KeyCollection.
OrderedDictionary.ValueCollection.Enumerator	Enumerates the elements of a OrderedDictionary.ValueCollection.
PriorityQueue.UnorderedItemsCollection.Enumerator	Enumerates the element and priority pairs of a PriorityQueue, without any ordering guarantees.
Queue.Enumerator	Enumerates the elements of a Queue.
SortedDictionary.Enumerator	Enumerates the elements of a SortedDictionary.
SortedDictionary.KeyCollection.Enumerator	Enumerates the elements of a SortedDictionary.KeyCollection.
SortedDictionary.ValueCollection.Enumerator	Enumerates the elements of a SortedDictionary.ValueCollection.
SortedSet.Enumerator	Enumerates the elements of a SortedSet object.
Stack.Enumerator	Enumerates the elements of a Stack.

Interfaces

Name	Description
IAlternateEqualityComparer	Implemented by an IEqualityComparer to support comparing a `TAlternate` instance with a `T` instance.
IAsyncEnumerable	Exposes an enumerator that provides asynchronous iteration over values of a specified type.
IAsyncEnumerator	Supports a simple asynchronous iteration over a generic collection.
ICollection	Defines methods to manipulate generic collections.
IComparer	Defines a method that a type implements to compare two objects.
IDictionary	Represents a generic collection of key/value pairs.
IEnumerable	Exposes the enumerator, which supports a simple iteration over a collection of a specified type.
IEnumerator	Supports a simple iteration over a generic collection.
IEqualityComparer	Defines methods to support the comparison of objects for equality.
IList	Represents a collection of objects that can be individually accessed by index.
IReadOnlyCollection	Represents a strongly-typed, read-only collection of elements.
IReadOnlyDictionary	Represents a generic read-only collection of key/value pairs.
IReadOnlyList	Represents a read-only collection of elements that can be accessed by index.
IReadOnlySet	Provides a readonly abstraction of a set.
ISet	Provides the base interface for the abstraction of sets.

Remarks

Many of the generic collection types are direct analogs of nongeneric types. Dictionary is a generic version of Hashtable; it uses the generic structure KeyValuePair for enumeration instead of DictionaryEntry. List is a generic version of ArrayList. There are generic Queue and Stack classes that correspond to the nongeneric versions. There are generic and nongeneric versions of SortedList. Both versions are hybrids of a dictionary and a list. The SortedDictionary generic class is a pure dictionary and has no nongeneric counterpart. The LinkedList generic class is a true linked list and has no nongeneric counterpart.

Feedback

Was this page helpful?