MoreEnumerableDistinctByTSource, TKey(IEnumerableTSource, FuncTSource, TKey, IEqualityComparerTKey) Method

Returns all distinct elements of the given source, where "distinctness" is determined via a projection and the specified comparer for the projected type.

Definition

Namespace: MoreLinq
Assembly: MoreLinq (in MoreLinq.dll) Version: 4.4.0+6d97c3b1d482f98300f4446df14742b0e3fafbec

C#

public static IEnumerable<TSource> DistinctBy<TSource, TKey>(
	IEnumerable<TSource> source,
	Func<TSource, TKey> keySelector,
	IEqualityComparer<TKey>? comparer
)

VB

Public Shared Function DistinctBy(Of TSource, TKey) ( 
	source As IEnumerable(Of TSource),
	keySelector As Func(Of TSource, TKey),
	comparer As IEqualityComparer(Of TKey)
) As IEnumerable(Of TSource)

C++

public:
generic<typename TSource, typename TKey>
static IEnumerable<TSource>^ DistinctBy(
	IEnumerable<TSource>^ source, 
	Func<TSource, TKey>^ keySelector, 
	IEqualityComparer<TKey>^ comparer
)

F#

static member DistinctBy : 
        source : IEnumerable<'TSource> * 
        keySelector : Func<'TSource, 'TKey> * 
        comparer : IEqualityComparer<'TKey> -> IEnumerable<'TSource>

Parameters

source IEnumerableTSource: Source sequence
keySelector FuncTSource, TKey: Projection for determining "distinctness"
comparer IEqualityComparerTKey: The equality comparer to use to determine whether or not keys are equal. If null, the default equality comparer for TSource is used.

Type Parameters

TSource: Type of the source sequence
TKey: Type of the projected element

Return Value

IEnumerableTSource
A sequence consisting of distinct elements from the source sequence, comparing them by the specified key projection.

Remarks

This operator uses deferred execution and streams the results, although a set of already-seen keys is retained. If a key is seen multiple times, only the first element with that key is returned.