Enumerable.TakeWhile Método

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ TakeWhile(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);

public static System.Collections.Generic.IEnumerable<TSource> TakeWhile<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);

static member TakeWhile : seq<'Source> * Func<'Source, bool> -> seq<'Source>

<Extension()>
Public Function TakeWhile(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As IEnumerable(Of TSource)

Parámetros de tipo

Parámetros

Devoluciones

IEnumerable<TSource>

IEnumerable<T> que contiene los elementos de la secuencia de entrada que se encuentran antes del elemento que no supera la prueba.An IEnumerable<T> that contains the elements from the input sequence that occur before the element at which the test no longer passes.

Excepciones

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) para devolver elementos desde el inicio de una secuencia siempre que se cumpla una condición.The following code example demonstrates how to use TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to return elements from the start of a sequence as long as a condition is true.

string[] fruits = { "apple", "banana", "mango", "orange",
                      "passionfruit", "grape" };

IEnumerable<string> query =
    fruits.TakeWhile(fruit => String.Compare("orange", fruit, true) != 0);

foreach (string fruit in query)
{
    Console.WriteLine(fruit);
}

/*
 This code produces the following output:

 apple
 banana
 mango
*/

' Create an array of strings.
Dim fruits() As String =
{"apple", "banana", "mango", "orange", "passionfruit", "grape"}

' Take strings from the array until one of
' the strings matches "orange".
Dim query As IEnumerable(Of String) =
fruits.TakeWhile(Function(fruit) _
                     String.Compare("orange", fruit, True) <> 0)

' Display the results.
Dim output As New System.Text.StringBuilder
For Each fruit As String In query
    output.AppendLine(fruit)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' apple
' banana
' mango

Comentarios

Este método se implementa mediante la ejecución aplazada.This method is implemented by using deferred execution. El valor devuelto inmediato es un objeto que almacena toda la información necesaria para realizar la acción.The immediate return value is an object that stores all the information that is required to perform the action. La consulta representada por este método no se ejecuta hasta que el objeto se enumera mediante una llamada a su GetEnumerator método directamente o mediante foreach en Visual C# o For Each en Visual Basic.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.

El TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) método prueba cada elemento de mediante source predicate y produce el elemento si el resultado es true .The TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) method tests each element of source by using predicate and yields the element if the result is true. La enumeración se detiene cuando la función de predicado devuelve false para un elemento o cuando source no contiene más elementos.Enumeration stops when the predicate function returns false for an element or when source contains no more elements.

Los TakeWhile SkipWhile métodos y son complementos funcionales.The TakeWhile and SkipWhile methods are functional complements. Dada una secuencia coll y una función pura p , la concatenación de los resultados de coll.TakeWhile(p) y coll.SkipWhile(p) produce la misma secuencia que coll .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.

En Visual Basic sintaxis de expresiones de consulta, una Take While cláusula se convierte en una invocación de TakeWhile .In Visual Basic query expression syntax, a Take While clause translates to an invocation of TakeWhile.

Consulte también

• Take While (Cláusula, Visual Basic)Take While Clause (Visual Basic)

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ TakeWhile(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, int, bool> ^ predicate);

public static System.Collections.Generic.IEnumerable<TSource> TakeWhile<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,bool> predicate);

static member TakeWhile : seq<'Source> * Func<'Source, int, bool> -> seq<'Source>

<Extension()>
Public Function TakeWhile(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Integer, Boolean)) As IEnumerable(Of TSource)

Parámetros de tipo

Parámetros

Devoluciones

IEnumerable<TSource>

IEnumerable<T> que contiene los elementos de la secuencia de entrada que se encuentran antes del elemento que no supera la prueba.An IEnumerable<T> that contains elements from the input sequence that occur before the element at which the test no longer passes.

Excepciones

Ejemplos

En el ejemplo de código siguiente se muestra cómo usar TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) para devolver elementos desde el inicio de una secuencia siempre que una condición que use el índice del elemento sea true.The following code example demonstrates how to use TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) to return elements from the start of a sequence as long as a condition that uses the element's index is true.

string[] fruits = { "apple", "passionfruit", "banana", "mango",
                      "orange", "blueberry", "grape", "strawberry" };

IEnumerable<string> query =
    fruits.TakeWhile((fruit, index) => fruit.Length >= index);

foreach (string fruit in query)
{
    Console.WriteLine(fruit);
}

/*
 This code produces the following output:

 apple
 passionfruit
 banana
 mango
 orange
 blueberry
*/

' Create an array of strings.
Dim fruits() As String =
{"apple", "passionfruit", "banana", "mango",
 "orange", "blueberry", "grape", "strawberry"}

' Take strings from the array until one
' of the string's lengths is greater than or
' equal to the string item's index in the array.
Dim query As IEnumerable(Of String) =
fruits.TakeWhile(Function(fruit, index) _
                     fruit.Length >= index)

' Display the results.
Dim output As New System.Text.StringBuilder
For Each fruit As String In query
    output.AppendLine(fruit)
Next
Console.WriteLine(output.ToString())

' This code produces the following output:
'
' apple
' passionfruit
' banana
' mango
' orange
' blueberry

Comentarios

Este método se implementa mediante la ejecución aplazada.This method is implemented by using deferred execution. El valor devuelto inmediato es un objeto que almacena toda la información necesaria para realizar la acción.The immediate return value is an object that stores all the information that is required to perform the action. La consulta representada por este método no se ejecuta hasta que el objeto se enumera mediante una llamada a su GetEnumerator método directamente o mediante foreach en Visual C# o For Each en Visual Basic.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.

El TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) método prueba cada elemento de mediante source predicate y produce el elemento si el resultado es true .The TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) method tests each element of source by using predicate and yields the element if the result is true. La enumeración se detiene cuando la función de predicado devuelve false para un elemento o cuando source no contiene más elementos.Enumeration stops when the predicate function returns false for an element or when source contains no more elements.

El primer argumento de predicate representa el elemento que se va a probar.The first argument of predicate represents the element to test. El segundo argumento representa el índice de base cero del elemento dentro de source .The second argument represents the zero-based index of the element within source.

Los TakeWhile SkipWhile métodos y son complementos funcionales.The TakeWhile and SkipWhile methods are functional complements. Dada una secuencia coll y una función pura p , la concatenación de los resultados de coll.TakeWhile(p) y coll.SkipWhile(p) produce la misma secuencia que coll .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.

En Visual Basic sintaxis de expresiones de consulta, una Take While cláusula se convierte en una invocación de TakeWhile .In Visual Basic query expression syntax, a Take While clause translates to an invocation of TakeWhile.

Consulte también

• Take While (Cláusula, Visual Basic)Take While Clause (Visual Basic)