Method TakeUntil

TakeUntil<TSource>(IEnumerable<TSource>, Func<TSource, bool>)

Takes items from the input sequence until the given predicate returns true when applied to the current source item; that item will be the last taken.

Declaration

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

Parameters

Type	Name	Description
IEnumerable<TSource>	source	Source sequence
Func<TSource, bool>	predicate	Predicate used to determine when to stop yielding results from the source.

Returns

Type	Description
IEnumerable<TSource>	Items from the source sequence until the predicate first returns true when applied to the item.

Type Parameters

Name	Description
TSource	Type of the source sequence

Remarks

TakeUntil differs from TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource, bool>) 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 returns the element which causes the predicate to return true.

This operator uses deferred execution and streams its result.

Examples

The following code example demonstrates how to take elements in a sequence until a condition is true using TakeUntil.

var sequence = Enumerable.Range(1, 10);

// Take elements until the condition is true
var result = sequence
    .TakeUntil(x => x == 5);

Console.WriteLine(
    "[" +
    string.Join(", ", result) +
    "]");

// This code produces the following output:
// [1, 2, 3, 4, 5]

Exceptions

Type	Condition
ArgumentNullException	source or predicate is null