Enumerable.Where Enumerable.Where Enumerable.Where Enumerable.Where Method

Definición

Filtra una secuencia de valores en función de un predicado.Filters a sequence of values based on a predicate.

Sobrecargas

Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Filtra una secuencia de valores en función de un predicado.Filters a sequence of values based on a predicate.

Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

Filtra una secuencia de valores en función de un predicado.Filters a sequence of values based on a predicate. El índice de cada elemento se usa en la lógica de la función de predicado.Each element's index is used in the logic of the predicate function.

Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)

Filtra una secuencia de valores en función de un predicado.Filters a sequence of values based on a predicate.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Where(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, bool> ^ predicate);
public static System.Collections.Generic.IEnumerable<TSource> Where<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,bool> predicate);
static member Where : seq<'Source> * Func<'Source, bool> -> seq<'Source>
<Extension()>
Public Function Where(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Boolean)) As IEnumerable(Of TSource)

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> que se va a filtrar.An IEnumerable<T> to filter.

predicate
Func<TSource,Boolean>

Función para probar cada elemento de una condición.A function to test each element for a condition.

Devoluciones

IEnumerable<TSource>

IEnumerable<T> que contiene los elementos de la secuencia de entrada que satisfacen la condición.An IEnumerable<T> that contains elements from the input sequence that satisfy the condition.

Excepciones

source o predicate es null.source or predicate is null.

Ejemplos

En el ejemplo de código siguiente se muestra Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) cómo utilizar para filtrar una secuencia.The following code example demonstrates how to use Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>) to filter a sequence.

List<string> fruits =
    new List<string> { "apple", "passionfruit", "banana", "mango", 
                    "orange", "blueberry", "grape", "strawberry" };

IEnumerable<string> query = fruits.Where(fruit => fruit.Length < 6);

foreach (string fruit in query)
{
    Console.WriteLine(fruit);
}
/*
 This code produces the following output:

 apple
 mango
 grape
*/
' Create a list of strings.
Dim fruits As New List(Of String)(New String() _
                    {"apple", "passionfruit", "banana", "mango",
                     "orange", "blueberry", "grape", "strawberry"})

' Restrict the results to those strings whose 
' length is less than six.
Dim query As IEnumerable(Of String) =
fruits.Where(Function(fruit) fruit.Length < 6)

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

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

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 llamando a GetEnumerator su método directamente o usando 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.

En la sintaxis de las expresiones where de consulta C#, una Where cláusula (visual) o (Visual Basic) se traduce en una Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)invocación de.In query expression syntax, a where (Visual C#) or Where (Visual Basic) clause translates to an invocation of Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>).

Consulte también:

Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)

Filtra una secuencia de valores en función de un predicado.Filters a sequence of values based on a predicate. El índice de cada elemento se usa en la lógica de la función de predicado.Each element's index is used in the logic of the predicate function.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TSource> ^ Where(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, int, bool> ^ predicate);
public static System.Collections.Generic.IEnumerable<TSource> Where<TSource> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,bool> predicate);
static member Where : seq<'Source> * Func<'Source, int, bool> -> seq<'Source>
<Extension()>
Public Function Where(Of TSource) (source As IEnumerable(Of TSource), predicate As Func(Of TSource, Integer, Boolean)) As IEnumerable(Of TSource)

Parámetros de tipo

TSource

Tipo de los elementos de source.The type of the elements of source.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> que se va a filtrar.An IEnumerable<T> to filter.

predicate
Func<TSource,Int32,Boolean>

Función que va a probar cada elemento de origen para determinar si satisface una condición; el segundo parámetro de la función representa el índice del elemento de origen.A function to test each source element for a condition; the second parameter of the function represents the index of the source element.

Devoluciones

IEnumerable<TSource>

IEnumerable<T> que contiene los elementos de la secuencia de entrada que satisfacen la condición.An IEnumerable<T> that contains elements from the input sequence that satisfy the condition.

Excepciones

source o predicate es null.source or predicate is null.

Ejemplos

En el ejemplo de código siguiente se muestra Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) cómo utilizar para filtrar una secuencia basada en un predicado que implique el índice de cada elemento.The following code example demonstrates how to use Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>) to filter a sequence based on a predicate that involves the index of each element.

int[] numbers = { 0, 30, 20, 15, 90, 85, 40, 75 };

IEnumerable<int> query =
    numbers.Where((number, index) => number <= index * 10);

foreach (int number in query)
{
    Console.WriteLine(number);
}
/*
 This code produces the following output:

 0
 20
 15
 40
*/
' Create an array of integers.
Dim numbers() As Integer = {0, 30, 20, 15, 90, 85, 40, 75}

' Restrict the results to those numbers whose
' values are less than or equal to their index times 10.
Dim query As IEnumerable(Of Integer) =
numbers.Where(Function(number, index) number <= index * 10)

' Display the results.
Dim output As New System.Text.StringBuilder
For Each number As Integer In query
    output.AppendLine(number)
Next
MsgBox(output.ToString())

' This code produces the following output:
'
' 0
' 20
' 15
' 40

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 llamando a GetEnumerator su método directamente o usando 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 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 sourcede.The second argument represents the zero-based index of the element within source.

Se aplica a