MoreEnumerableTakeUntilTSource Method

public static IEnumerable<TSource> TakeUntil<TSource>(
	this IEnumerable<TSource> source,
	Func<TSource, bool> predicate
)

<ExtensionAttribute>
Public Shared Function TakeUntil(Of TSource) ( 
	source As IEnumerable(Of TSource),
	predicate As Func(Of TSource, Boolean)
) As IEnumerable(Of TSource)

public:
[ExtensionAttribute]
generic<typename TSource>
static IEnumerable<TSource>^ TakeUntil(
	IEnumerable<TSource>^ source, 
	Func<TSource, bool>^ predicate
)

[<ExtensionAttribute>]
static member TakeUntil : 
        source : IEnumerable<'TSource> * 
        predicate : Func<'TSource, bool> -> IEnumerable<'TSource> 

Parameters

source  IEnumerableTSource

Source sequence

predicate  FuncTSource, Boolean

Predicate used to determine when to stop yielding results from the source.

Type Parameters

TSource

Type of the source sequence

Return Value

Usage Note

TakeUntil differs from Enumerable.TakeWhile in two respects. Firstly, the sense of the predicate is reversed: it is expected that the predicate will return false to start with, and then return true - for example, when trying to find a matching item in a sequence.

Secondly, TakeUntil yields the element which causes the predicate to return true. For example, in a sequence

{ 1, 2, 3, 4, 5 }

x => x == 3

{ 1, 2, 3 }

TakeUntil is as lazy as possible: it will not iterate over the source sequence until it has to, it won't iterate further than it has to, and it won't evaluate the predicate until it has to. (This means that an item may be returned which would actually cause the predicate to throw an exception if it were evaluated, so long as no more items of data are requested.)

Reference