Enumerable.TakeWhile<'TSource> Method (IEnumerable<'TSource>, Func<'TSource, Boolean>)
Returns elements from a sequence as long as a specified condition is true.
Assembly: System.Core (in System.Core.dll)
static member TakeWhile<'TSource> : source:IEnumerable<'TSource> * predicate:Func<'TSource, bool> -> IEnumerable<'TSource>
A sequence to return elements from.
Return ValueType: System.Collections.Generic.IEnumerable<'TSource>
An IEnumerable<'T> that contains the elements from the input sequence that occur before the element at which the test no longer passes.
The type of the elements of source.
This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.
Themethod tests each element of source by using predicate and yields the element if the result is true. Enumeration stops when the predicate function returns false for an element or when source contains no more elements.
The TakeWhile and SkipWhile methods are functional complements. Given a sequence coll and a pure function p, concatenating the results of coll.TakeWhile(p) and coll.SkipWhile(p) yields the same sequence as coll.
In Visual Basic query expression syntax, a Take While clause translates to an invocation of TakeWhile.
Available since 8
Available since 3.5
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Available since 8.1