ILookup<TKey, TElement> Interface

System.Linq

Represents a collection of elements, grouped by a specified key.

Remarks

The ILookup<TKey, TElement> interface is implemented by the objects that result from a call to the GroupBy extension method. It represents a collection of groups, where each group is identified by a key and contains a sequence of elements that share that key.

ILookup<TKey, TElement> is read-only. It is designed to be an efficient way to represent the results of grouping operations, providing fast lookups of elements by their key.

Type Parameters

TKey: The type of the keys of the elements in the collection.

TElement: The type of the elements in the collection.

Members

Count

int Count { get; }

Gets the number of keys in the lookup collection.
Item[TKey key]

IEnumerable<TElement> this[TKey key] { get; }

Gets the sequence of elements that have the specified key in the lookup collection.

Parameters

key

The key of the elements to retrieve.

Methods

Contains

bool Contains(TKey key)

Determines whether the lookup collection contains elements for the specified key.

Parameters

key

The key to search for.

Returns

true if the lookup collection contains elements associated with the specified key; otherwise, false.
GetEnumerator

IEnumerator<KeyValuePair<TKey, IEnumerable<TElement>>> GetEnumerator()

Returns an enumerator that iterates through the lookup collection.

Returns

An enumerator that iterates through the lookup collection.
GetEnumerator

IEnumerator GetEnumerator()

Returns an enumerator that iterates through the lookup collection.

Returns

An enumerator that iterates through the lookup collection.
GetGroupEnumerable

IEnumerable<TElement> GetGroupEnumerable(TKey key)

Gets the sequence of elements that have the specified key in the lookup collection.

Parameters

key

The key of the elements to retrieve.

Returns

A sequence of elements that have the specified key.

Inheritance

ILookup<TKey, TElement> inherits from:

ILookup<TKey, TElement> Interface

Remarks

Parameters

Parameters

Returns

Returns

Returns

Parameters

Returns