DistinctByExtensionDistinctByTSource, 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.Extensions
Assembly: MoreLinq (in MoreLinq.dll) Version: 4.1.0+0e154ef592f33ce0f6f3d534a9eedee273f0ce72

C#

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

VB

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

F#

[<ExtensionAttribute>]
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.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerableTSource. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).

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.