Enumerable.CountBy<TSource,TKey> Method

Reference

Definition

Namespace:: System.Linq

Assemblies:: netstandard.dll, System.Linq.dll

Source:: CountBy.cs

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.

Returns the count of elements in the source sequence grouped by key.

public static System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<TKey,int>> CountBy<TSource,TKey>(this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IEqualityComparer<TKey>? keyComparer = default);

static member CountBy : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<System.Collections.Generic.KeyValuePair<'Key, int>>

<Extension()>
Public Function CountBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), Optional keyComparer As IEqualityComparer(Of TKey) = Nothing) As IEnumerable(Of KeyValuePair(Of TKey, Integer))

Type Parameters

TSource

The type of elements of source.

TKey

The type of the key returned by keySelector.

Parameters

source: IEnumerable<TSource>

A sequence that contains elements to be counted.

keySelector: Func<TSource,TKey>

A function to extract the key for each element.

keyComparer: IEqualityComparer<TKey>

An IEqualityComparer<T> to compare keys with.

Returns

IEnumerable<KeyValuePair<TKey,Int32>>

An enumerable containing the frequencies of each key occurrence in source.

Applies to

Produkt	Versioner
.NET	9, 10

Dela via