Enumerable.CountBy<TSource,TKey> Method
Definition
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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
An enumerable containing the frequencies of each key occurrence in source.
Applies to
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