Enumerable.GroupBy Enumerable.GroupBy Enumerable.GroupBy Enumerable.GroupBy Method

Definición

Agrupa los elementos de una secuencia.Groups the elements of a sequence.

Sobrecargas

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Los elementos de cada grupo se proyectan utilizando una función determinada.The elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Los valores de las claves se comparan utilizando un comparador especificado y los elementos de cada grupo se proyectan utilizando una función especificada.Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y proyecta los elementos de cada grupo utilizando una función determinada.Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia conforme a una función del selector de claves.Groups the elements of a sequence according to a key selector function. Las claves se comparan utilizando un comparador y los elementos de cada grupo se proyectan utilizando una función especificada.The keys are compared by using a comparer and each group's elements are projected by using a specified function.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Las claves se comparan utilizando un comparador especificado.The keys are compared by using a specified comparer.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada.Groups the elements of a sequence according to a specified key selector function.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y compara las claves utilizando un comparador especificado.Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Los elementos de cada grupo se proyectan utilizando una función determinada.The elements of each group are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult> resultSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * Func<'Key, seq<'Element>, 'Result> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), resultSelector As Func(Of TKey, IEnumerable(Of TElement), TResult)) As IEnumerable(Of TResult)

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TElement

Tipo de los elementos de cada IGrouping<TKey,TElement>.The type of the elements in each IGrouping<TKey,TElement>.

TResult

Tipo del valor de resultado devuelto por resultSelector.The type of the result value returned by resultSelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

Función que asigna cada elemento de origen a un elemento de IGrouping<TKey,TElement>.A function to map each source element to an element in an IGrouping<TKey,TElement>.

resultSelector
Func<TKey,IEnumerable<TElement>,TResult>

Función que va a crear un valor de resultado a partir de cada grupo.A function to create a result value from each group.

Devoluciones

IEnumerable<TResult>

Colección de elementos de tipo TResult donde cada elemento representa una proyección sobre un grupo y su clave.A collection of elements of type TResult where each element represents a projection over a group and its key.

Ejemplos

En el ejemplo de código siguiente se muestra GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) cómo usar para agrupar los elementos proyectados de una secuencia y, a continuación, TResultproyectar una secuencia de resultados de tipo.The following code example demonstrates how to use GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) to group the projected elements of a sequence and then project a sequence of results of type TResult.

class Pet
{
    public string Name { get; set; }
    public double Age { get; set; }
}

public static void GroupByEx4()
{
    // Create a list of pets.
    List<Pet> petsList =
        new List<Pet>{ new Pet { Name="Barley", Age=8.3 },
                       new Pet { Name="Boots", Age=4.9 },
                       new Pet { Name="Whiskers", Age=1.5 },
                       new Pet { Name="Daisy", Age=4.3 } };

    // Group Pet.Age values by the Math.Floor of the age.
    // Then project an anonymous type from each group
    // that consists of the key, the count of the group's
    // elements, and the minimum and maximum age in the group.
    var query = petsList.GroupBy(
        pet => Math.Floor(pet.Age),
        pet => pet.Age,
        (baseAge, ages) => new
        {
            Key = baseAge,
            Count = ages.Count(),
            Min = ages.Min(),
            Max = ages.Max()
        });

    // Iterate over each anonymous type.
    foreach (var result in query)
    {
        Console.WriteLine("\nAge group: " + result.Key);
        Console.WriteLine("Number of pets in this age group: " + result.Count);
        Console.WriteLine("Minimum age: " + result.Min);
        Console.WriteLine("Maximum age: " + result.Max);
    }

    /*  This code produces the following output:
     
        Age group: 8
        Number of pets in this age group: 1
        Minimum age: 8.3
        Maximum age: 8.3
     
        Age group: 4
        Number of pets in this age group: 2
        Minimum age: 4.3
        Maximum age: 4.9
     
        Age group: 1
        Number of pets in this age group: 1
        Minimum age: 1.5
        Maximum age: 1.5
    */
}
Structure Pet
    Public Name As String
    Public Age As Double
End Structure

Public Sub GroupByEx4()
    ' Create a list of pets.
    Dim petsList As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8.3},
                          New Pet With {.Name = "Boots", .Age = 4.9},
                          New Pet With {.Name = "Whiskers", .Age = 1.5},
                          New Pet With {.Name = "Daisy", .Age = 4.3}})

    ' Group Pet.Age values by the Math.Floor of the age.
    ' Then project an anonymous type from each group
    ' that consists of the key, the count of the group's
    ' elements, and the minimum and maximum age in the group.
    Dim query = petsList.GroupBy(
Function(pet) Math.Floor(pet.Age),
Function(pet) pet.Age,
Function(baseAge, ages) New With
    {.Key = baseAge,
    .Count = ages.Count(),
    .Min = ages.Min(),
    .Max = ages.Max()}
)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each anonymous type.
    For Each result In query
        output.AppendLine(vbCrLf & "Age group: " & result.Key)
        output.AppendLine("Number of pets in this age group: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

    ' Display the output.
    MsgBox(output.ToString)
End Sub

' This code produces the following output:

' Age group: 8
' Number of pets in this age group: 1
' Minimum age: 8.3
' Maximum age: 8.3
'
' Age group: 4
' Number of pets in this age group: 2
' Minimum age: 4.3
' Maximum age: 4.9
'
' Age group: 1
' Number of pets in this age group: 1
' Minimum age: 1.5
' Maximum age: 1.5

Comentarios

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy.

Consulte también:

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Los valores de las claves se comparan utilizando un comparador especificado y los elementos de cada grupo se proyectan utilizando una función especificada.Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * Func<'Key, seq<'Element>, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), resultSelector As Func(Of TKey, IEnumerable(Of TElement), TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TElement

Tipo de los elementos de cada IGrouping<TKey,TElement>.The type of the elements in each IGrouping<TKey,TElement>.

TResult

Tipo del valor de resultado devuelto por resultSelector.The type of the result value returned by resultSelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

Función que asigna cada elemento de origen a un elemento de IGrouping<TKey,TElement>.A function to map each source element to an element in an IGrouping<TKey,TElement>.

resultSelector
Func<TKey,IEnumerable<TElement>,TResult>

Función que va a crear un valor de resultado a partir de cada grupo.A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

Interfaz IEqualityComparer<T> con la que se van a comparar las claves.An IEqualityComparer<T> to compare keys with.

Devoluciones

IEnumerable<TResult>

Colección de elementos de tipo TResult donde cada elemento representa una proyección sobre un grupo y su clave.A collection of elements of type TResult where each element represents a projection over a group and its key.

Consulte también:

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y proyecta los elementos de cada grupo utilizando una función determinada.Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TElement> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> -> seq<System.Linq.IGrouping<'Key, 'Element>>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement)) As IEnumerable(Of IGrouping(Of TKey, TElement))

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TElement

Tipo de los elementos de IGrouping<TKey,TElement>.The type of the elements in the IGrouping<TKey,TElement>.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

Función que asigna cada elemento de origen a un elemento de IGrouping<TKey,TElement>.A function to map each source element to an element in the IGrouping<TKey,TElement>.

Devoluciones

IEnumerable<IGrouping<TKey,TElement>>

IEnumerable<IGrouping<TKey, TElement>> en C# o IEnumerable(Of IGrouping(Of TKey, TElement)) en Visual Basic donde cada objeto IGrouping<TKey,TElement> contiene una colección de objetos de tipo TElement y una clave.An IEnumerable<IGrouping<TKey, TElement>> in C# or IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects of type TElement and a key.

Excepciones

source o keySelector o elementSelector es null.source or keySelector or elementSelector is null.

Ejemplos

En el ejemplo de código siguiente se muestra GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) cómo usar para agrupar los elementos de una secuencia.The following code example demonstrates how to use GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) to group the elements of a sequence.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

// Uses method-based query syntax.
public static void GroupByEx1()
{
    // Create a list of pets.
    List<Pet> pets =
        new List<Pet>{ new Pet { Name="Barley", Age=8 },
                       new Pet { Name="Boots", Age=4 },
                       new Pet { Name="Whiskers", Age=1 },
                       new Pet { Name="Daisy", Age=4 } };

    // Group the pets using Age as the key value 
    // and selecting only the pet's Name for each value.
    IEnumerable<IGrouping<int, string>> query =
        pets.GroupBy(pet => pet.Age, pet => pet.Name);

    // Iterate over each IGrouping in the collection.
    foreach (IGrouping<int, string> petGroup in query)
    {
        // Print the key value of the IGrouping.
        Console.WriteLine(petGroup.Key);
        // Iterate over each value in the 
        // IGrouping and print the value.
        foreach (string name in petGroup)
            Console.WriteLine("  {0}", name);
    }
}

/*
 This code produces the following output:

 8
   Barley
 4
   Boots
   Daisy
 1
   Whiskers
*/
Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Sub GroupByEx1()
    'Create a list of Pet objects.
    Dim pets As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8},
                          New Pet With {.Name = "Boots", .Age = 4},
                          New Pet With {.Name = "Whiskers", .Age = 1},
                          New Pet With {.Name = "Daisy", .Age = 4}})

    ' Group the pets using Age as the key 
    ' and selecting only the pet's Name for each value.
    Dim query As IEnumerable(Of IGrouping(Of Integer, String)) =
pets.GroupBy(Function(pet) pet.Age,
             Function(pet) pet.Name)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each IGrouping in the collection.
    For Each petGroup As IGrouping(Of Integer, String) In query
        ' Print the key value of the IGrouping.
        output.AppendLine(petGroup.Key)
        ' Iterate over each value in the IGrouping and print the value.
        For Each name As String In petGroup
            output.AppendLine("  " & name)
        Next
    Next

    ' Display the output.
    MsgBox(output.ToString)
End Sub

' This code produces the following output:
'
' 8
'   Barley
' 4
'   Boots
'   Daisy
' 1
'   Whiskers

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. La traducción de la expresión de consulta en el ejemplo siguiente es equivalente a la consulta del ejemplo anterior.The translation of the query expression in the following example is equivalent to the query in the example above.

IEnumerable<IGrouping<int, string>> query =
    from pet in pets
    group pet.Name by pet.Age;
    Dim query =
From pet In pets
Group pet.Name By Age = pet.Age Into ageGroup = Group

Nota

En una expresión C# de consulta visual o Visual Basic, las expresiones de selección de elementos y claves se producen en el orden inverso al de sus posiciones GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) de argumentos en una llamada al método.In a Visual C# or Visual Basic query expression, the element and key selection expressions occur in the reverse order from their argument positions in a call to the GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method.

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 GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) método devuelve una colección de IGrouping<TKey,TElement> objetos, uno para cada clave distinta que se encontró.The GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. Un IGrouping<TKey,TElement> es un IEnumerable<T> objeto que también tiene una clave asociada a sus elementos.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Los IGrouping<TKey,TElement> objetos se producen en un orden basado en el orden de los elementos de source que generaron la primera clave de cada IGrouping<TKey,TElement>.The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. Los elementos de una agrupación se producen en el orden en sourceque aparecen los elementos que los generan.Elements in a grouping are yielded in the order that the elements that produced them appear in source.

El comparador de Default igualdad predeterminado se usa para comparar claves.The default equality comparer Default is used to compare keys.

Consulte también:

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia conforme a una función del selector de claves.Groups the elements of a sequence according to a key selector function. Las claves se comparan utilizando un comparador y los elementos de cada grupo se proyectan utilizando una función especificada.The keys are compared by using a comparer and each group's elements are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TElement> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<System.Linq.IGrouping<'Key, 'Element>>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of IGrouping(Of TKey, TElement))

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TElement

Tipo de los elementos de IGrouping<TKey,TElement>.The type of the elements in the IGrouping<TKey,TElement>.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

Función que asigna cada elemento de origen a un elemento de IGrouping<TKey,TElement>.A function to map each source element to an element in an IGrouping<TKey,TElement>.

comparer
IEqualityComparer<TKey>

IEqualityComparer<T> para comparar claves.An IEqualityComparer<T> to compare keys.

Devoluciones

IEnumerable<IGrouping<TKey,TElement>>

IEnumerable<IGrouping<TKey, TElement>> en C# o IEnumerable(Of IGrouping(Of TKey, TElement)) en Visual Basic donde cada objeto IGrouping<TKey,TElement> contiene una colección de objetos de tipo TElement y una clave.An IEnumerable<IGrouping<TKey, TElement>> in C# or IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects of type TElement and a key.

Excepciones

source o keySelector o elementSelector es null.source or keySelector or elementSelector is null.

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 GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) método devuelve una colección de IGrouping<TKey,TElement> objetos, uno para cada clave distinta que se encontró.The GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. Un IGrouping<TKey,TElement> es un IEnumerable<T> objeto que también tiene una clave asociada a sus elementos.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Los IGrouping<TKey,TElement> objetos se producen en un orden basado en el orden de los elementos de source que generaron la primera clave de cada IGrouping<TKey,TElement>.The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. Los elementos de una agrupación se producen en el orden en sourceque aparecen los elementos que los generan.Elements in a grouping are yielded in the order that the elements that produced them appear in source.

Si comparer Default es null, se utiliza el comparador de igualdad predeterminado para comparar las claves.If comparer is null, the default equality comparer Default is used to compare keys.

Si dos claves se consideran iguales según comparer, se elige la primera clave como clave para esa agrupación.If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Para obtener más información y ejemplos de uso, vea cláusula Group y Group by.For more information and usage examples, see group clause and Group By Clause.

Consulte también:

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

public:
generic <typename TSource, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TKey, System::Collections::Generic::IEnumerable<TSource> ^, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TKey,System.Collections.Generic.IEnumerable<TSource>,TResult> resultSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Key, seq<'Source>, 'Result> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), resultSelector As Func(Of TKey, IEnumerable(Of TSource), TResult)) As IEnumerable(Of TResult)

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TResult

Tipo del valor de resultado devuelto por resultSelector.The type of the result value returned by resultSelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

resultSelector
Func<TKey,IEnumerable<TSource>,TResult>

Función que va a crear un valor de resultado a partir de cada grupo.A function to create a result value from each group.

Devoluciones

IEnumerable<TResult>

Colección de elementos de tipo TResult donde cada elemento representa una proyección sobre un grupo y su clave.A collection of elements of type TResult where each element represents a projection over a group and its key.

Ejemplos

En el ejemplo de código siguiente se muestra GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) cómo usar para agrupar los elementos de una secuencia y proyectar una secuencia TResultde resultados de tipo.The following code example demonstrates how to use GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) to group the elements of a sequence and project a sequence of results of type TResult.

class Pet
{
    public string Name { get; set; }
    public double Age { get; set; }
}

public static void GroupByEx3()
{
    // Create a list of pets.
    List<Pet> petsList =
        new List<Pet>{ new Pet { Name="Barley", Age=8.3 },
                       new Pet { Name="Boots", Age=4.9 },
                       new Pet { Name="Whiskers", Age=1.5 },
                       new Pet { Name="Daisy", Age=4.3 } };

    // Group Pet objects by the Math.Floor of their age.
    // Then project an anonymous type from each group
    // that consists of the key, the count of the group's
    // elements, and the minimum and maximum age in the group.
    var query = petsList.GroupBy(
        pet => Math.Floor(pet.Age),
        (age, pets) => new
        {
            Key = age,
            Count = pets.Count(),
            Min = pets.Min(pet => pet.Age),
            Max = pets.Max(pet => pet.Age)
        });

    // Iterate over each anonymous type.
    foreach (var result in query)
    {
        Console.WriteLine("\nAge group: " + result.Key);
        Console.WriteLine("Number of pets in this age group: " + result.Count);
        Console.WriteLine("Minimum age: " + result.Min);
        Console.WriteLine("Maximum age: " + result.Max);
    }

    /*  This code produces the following output:
     
        Age group: 8
        Number of pets in this age group: 1
        Minimum age: 8.3
        Maximum age: 8.3
     
        Age group: 4
        Number of pets in this age group: 2
        Minimum age: 4.3
        Maximum age: 4.9
     
        Age group: 1
        Number of pets in this age group: 1
        Minimum age: 1.5
        Maximum age: 1.5
    */
}
Structure Pet
    Public Name As String
    Public Age As Double
End Structure

Public Sub GroupByEx3()
    ' Create a list of pets.
    Dim petsList As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8.3},
                          New Pet With {.Name = "Boots", .Age = 4.9},
                          New Pet With {.Name = "Whiskers", .Age = 1.5},
                          New Pet With {.Name = "Daisy", .Age = 4.3}})

    ' Group Pet objects by the Math.Floor of their age.
    ' Then project an anonymous type from each group
    ' that consists of the key, the count of the group's
    ' elements, and the minimum and maximum age in the group.
    Dim query = petsList.GroupBy(
Function(pet) Math.Floor(pet.Age),
Function(age, pets) New With
    {.Key = age,
    .Count = pets.Count(),
    .Min = pets.Min(Function(pet) pet.Age),
    .Max = pets.Max(Function(Pet) Pet.Age)}
)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each anonymous type.
    For Each result In query
        output.AppendLine(vbCrLf & "Age group: " & result.Key)
        output.AppendLine("Number of pets in this age group: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

    ' Display the output.
    MsgBox(output.ToString)
End Sub

' This code produces the following output:

' Age group: 8
' Number of pets in this age group: 1
' Minimum age: 8.3
' Maximum age: 8.3
'
' Age group: 4
' Number of pets in this age group: 2
' Minimum age: 4.3
' Maximum age: 4.9
'
' Age group: 1
' Number of pets in this age group: 1
' Minimum age: 1.5
' Maximum age: 1.5

Comentarios

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy.

Consulte también:

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>) GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y crea un valor de resultado a partir de cada grupo y su clave.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Las claves se comparan utilizando un comparador especificado.The keys are compared by using a specified comparer.

public:
generic <typename TSource, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TKey, System::Collections::Generic::IEnumerable<TSource> ^, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TKey,System.Collections.Generic.IEnumerable<TSource>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Key, seq<'Source>, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), resultSelector As Func(Of TKey, IEnumerable(Of TSource), TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

TResult

Tipo del valor de resultado devuelto por resultSelector.The type of the result value returned by resultSelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

resultSelector
Func<TKey,IEnumerable<TSource>,TResult>

Función que va a crear un valor de resultado a partir de cada grupo.A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

Interfaz IEqualityComparer<T> con la que se van a comparar las claves.An IEqualityComparer<T> to compare keys with.

Devoluciones

IEnumerable<TResult>

Colección de elementos de tipo TResult donde cada elemento representa una proyección sobre un grupo y su clave.A collection of elements of type TResult where each element represents a projection over a group and its key.

Consulte también:

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada.Groups the elements of a sequence according to a specified key selector function.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> -> seq<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As IEnumerable(Of IGrouping(Of TKey, TSource))

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

Devoluciones

IEnumerable<IGrouping<TKey,TSource>>

IEnumerable<IGrouping<TKey, TSource>> en C# o IEnumerable(Of IGrouping(Of TKey, TSource)) en Visual Basic donde cada objeto IGrouping<TKey,TElement> contiene una secuencia de objetos y una clave.An IEnumerable<IGrouping<TKey, TSource>> in C# or IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> object contains a sequence of objects and a key.

Excepciones

source o keySelector es null.source or keySelector is null.

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 GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) método devuelve una colección de IGrouping<TKey,TElement> objetos, uno para cada clave distinta que se encontró.The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. Un IGrouping<TKey,TElement> es un IEnumerable<T> objeto que también tiene una clave asociada a sus elementos.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Los IGrouping<TKey,TElement> objetos se producen en un orden basado en el orden de los elementos de source que generaron la primera clave de cada IGrouping<TKey,TElement>.The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. Los elementos de una agrupación se producen en el orden en que aparecen sourceen.Elements in a grouping are yielded in the order they appear in source.

El comparador de Default igualdad predeterminado se usa para comparar claves.The default equality comparer Default is used to compare keys.

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Para obtener más información y ejemplos de uso, vea cláusula Group y Group by.For more information and usage examples, see group clause and Group By Clause.

Consulte también:

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

Agrupa los elementos de una secuencia según una función del selector de claves especificada y compara las claves utilizando un comparador especificado.Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of IGrouping(Of TKey, TSource))

Parámetros de tipo

TSource

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

TKey

Tipo de la clave devuelta por keySelector.The type of the key returned by keySelector.

Parámetros

source
IEnumerable<TSource>

IEnumerable<T> cuyos elementos se van a agrupar.An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

Función para extraer la clave de cada elemento.A function to extract the key for each element.

comparer
IEqualityComparer<TKey>

IEqualityComparer<T> para comparar claves.An IEqualityComparer<T> to compare keys.

Devoluciones

IEnumerable<IGrouping<TKey,TSource>>

IEnumerable<IGrouping<TKey, TSource>> en C# o IEnumerable(Of IGrouping(Of TKey, TSource)) en Visual Basic donde cada objeto IGrouping<TKey,TElement> contiene una colección de objetos y una clave.An IEnumerable<IGrouping<TKey, TSource>> in C# or IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects and a key.

Excepciones

source o keySelector es null.source or keySelector is null.

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 GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) método devuelve una colección de IGrouping<TKey,TElement> objetos, uno para cada clave distinta que se encontró.The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. Un IGrouping<TKey,TElement> es un IEnumerable<T> objeto que también tiene una clave asociada a sus elementos.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Los IGrouping<TKey,TElement> objetos se producen en un orden basado en el orden de los elementos de source que generaron la primera clave de cada IGrouping<TKey,TElement>.The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. Los elementos de una agrupación se producen en el orden en que aparecen sourceen.Elements in a grouping are yielded in the order they appear in source.

Si comparer Default es null, se utiliza el comparador de igualdad predeterminado para comparar las claves.If comparer is null, the default equality comparer Default is used to compare keys.

Si dos claves se consideran iguales según comparer, se elige la primera clave como clave para esa agrupación.If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

En la sintaxis de las expresiones group by de consulta C#, una Group By Into cláusula (visual) o (Visual Basic) se traduce en una GroupByinvocación de.In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Para obtener más información y ejemplos de uso, vea cláusula Group y Group by.For more information and usage examples, see group clause and Group By Clause.

Consulte también:

Se aplica a