Enumerable.ToLookup Method

Definition

Crea un objeto Lookup<TKey,TElement> genérico a partir de un objeto IEnumerable<T>.Creates a generic Lookup<TKey,TElement> from an IEnumerable<T>.

Overloads

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según el selector de claves especificado y las funciones del selector de elementos.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según una función del selector de claves, un comparador y una función del selector de elementos especificados.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.

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

Crea una clase Lookup<TKey,TElement> a partir de una interfaz IEnumerable<T> según una función del selector de claves especificada.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según una función del selector de claves especificada y el comparador de claves.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según el selector de claves especificado y las funciones del selector de elementos.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.

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

Type Parameters

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 valor devuelto por elementSelector.The type of the value returned by elementSelector.

Parameters

source
IEnumerable<TSource>

IEnumerable<T> a partir del cual se va a crear Lookup<TKey,TElement>.The IEnumerable<T> to create a Lookup<TKey,TElement> from.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de cada elemento.A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

Función de transformación que va a generar un valor de elemento de resultado a partir de cada elemento.A transform function to produce a result element value from each element.

Returns

ILookup<TKey,TElement>

Lookup<TKey,TElement> que contiene valores de tipo TElement seleccionados en la secuencia de entrada.A Lookup<TKey,TElement> that contains values of type TElement selected from the input sequence.

Exceptions

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

Examples

En el ejemplo de código siguiente se muestra cómo utilizar ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) para crear un Lookup<TKey,TElement> mediante una función del selector de claves y una función del selector de elementos.The following code example demonstrates how to use ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) to create a Lookup<TKey,TElement> by using a key selector function and an element selector function.

class Package
{
    public string Company { get; set; }
    public double Weight { get; set; }
    public long TrackingNumber { get; set; }
}

public static void ToLookupEx1()
{
    // Create a list of Packages.
    List<Package> packages =
        new List<Package>
            { new Package { Company = "Coho Vineyard",
                  Weight = 25.2, TrackingNumber = 89453312L },
              new Package { Company = "Lucerne Publishing",
                  Weight = 18.7, TrackingNumber = 89112755L },
              new Package { Company = "Wingtip Toys",
                  Weight = 6.0, TrackingNumber = 299456122L },
              new Package { Company = "Contoso Pharmaceuticals",
                  Weight = 9.3, TrackingNumber = 670053128L },
              new Package { Company = "Wide World Importers",
                  Weight = 33.8, TrackingNumber = 4665518773L } };

    // Create a Lookup to organize the packages.
    // Use the first character of Company as the key value.
    // Select Company appended to TrackingNumber
    // as the element values of the Lookup.
    ILookup<char, string> lookup =
        packages
        .ToLookup(p => Convert.ToChar(p.Company.Substring(0, 1)),
                  p => p.Company + " " + p.TrackingNumber);

    // Iterate through each IGrouping in the Lookup.
    foreach (IGrouping<char, string> packageGroup in lookup)
    {
        // Print the key value of the IGrouping.
        Console.WriteLine(packageGroup.Key);
        // Iterate through each value in the
        // IGrouping and print its value.
        foreach (string str in packageGroup)
            Console.WriteLine("    {0}", str);
    }
}

/*
 This code produces the following output:

 C
     Coho Vineyard 89453312
     Contoso Pharmaceuticals 670053128
 L
     Lucerne Publishing 89112755
 W
     Wingtip Toys 299456122
     Wide World Importers 4665518773
*/
Structure Package
    Public Company As String
    Public Weight As Double
    Public TrackingNumber As Long
End Structure

Sub ToLookupEx1()
    ' Create a list of Packages.
    Dim packages As New List(Of Package)(New Package() _
     {New Package With
      {.Company = "Coho Vineyard", .Weight = 25.2, .TrackingNumber = 89453312L},
      New Package With
      {.Company = "Lucerne Publishing", .Weight = 18.7, .TrackingNumber = 89112755L},
      New Package With
      {.Company = "Wingtip Toys", .Weight = 6.0, .TrackingNumber = 299456122L},
      New Package With
      {.Company = "Contoso Pharmaceuticals", .Weight = 9.3, .TrackingNumber = 670053128L},
      New Package With
      {.Company = "Wide World Importers", .Weight = 33.8, .TrackingNumber = 4665518773L}})

    ' Create a Lookup to organize the packages. 
    ' Use the first character of Company as the key value.
    ' Select Company appended to TrackingNumber 
    ' as the element values of the Lookup.
    Dim lookup As ILookup(Of Char, String) =
    packages.ToLookup(Function(p) _
                          Convert.ToChar(p.Company.Substring(0, 1)),
                      Function(p) _
                          p.Company & " " & p.TrackingNumber)

    Dim output As New System.Text.StringBuilder

    ' Iterate through each IGrouping in the Lookup.
    For Each packageGroup As IGrouping(Of Char, String) In lookup
        ' Print the key value of the IGrouping.
        output.AppendLine(packageGroup.Key)
        ' Iterate through each value in the IGrouping and print its value.
        For Each str As String In packageGroup
            output.AppendLine("   " & str)
        Next
    Next

    ' Select a group of packages by indexing directly into the Lookup.
    Dim cgroup As IEnumerable(Of String) = lookup("C"c)

    output.AppendLine(vbCrLf & "Packages from Company names that start with 'C':")
    For Each str As String In cgroup
        output.AppendLine(str)
    Next

    ' Display the output.
    Console.WriteLine(output.ToString())
End Sub

' This code produces the following output:
'
' C
'    Coho Vineyard 89453312
'    Contoso Pharmaceuticals 670053128
' L
'    Lucerne Publishing 89112755
' W
'    Wingtip Toys 299456122
'    Wide World Importers 4665518773
'
' Packages from Company names that start with 'C':
' Coho Vineyard 89453312
' Contoso Pharmaceuticals 670053128

Remarks

El método ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) devuelve un Lookup<TKey,TElement>, un diccionario uno a varios que asigna claves a colecciones de valores.The ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Un Lookup<TKey,TElement> difiere de un Dictionary<TKey,TValue>, que realiza una asignación uno a uno de claves a valores únicos.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

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

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según una función del selector de claves, un comparador y una función del selector de elementos especificados.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.

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

Type Parameters

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 valor devuelto por elementSelector.The type of the value returned by elementSelector.

Parameters

source
IEnumerable<TSource>

IEnumerable<T> a partir del cual se va a crear Lookup<TKey,TElement>.The IEnumerable<T> to create a Lookup<TKey,TElement> from.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de cada elemento.A function to extract a key from each element.

elementSelector
Func<TSource,TElement>

Función de transformación que va a generar un valor de elemento de resultado a partir de cada elemento.A transform function to produce a result element value from each element.

comparer
IEqualityComparer<TKey>

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

Returns

ILookup<TKey,TElement>

Lookup<TKey,TElement> que contiene valores de tipo TElement seleccionados en la secuencia de entrada.A Lookup<TKey,TElement> that contains values of type TElement selected from the input sequence.

Exceptions

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

Remarks

El método ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) devuelve un Lookup<TKey,TElement>, un diccionario uno a varios que asigna claves a colecciones de valores.The ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Un Lookup<TKey,TElement> difiere de un Dictionary<TKey,TValue>, que realiza una asignación uno a uno de claves a valores únicos.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

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

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

Crea una clase Lookup<TKey,TElement> a partir de una interfaz IEnumerable<T> según una función del selector de claves especificada.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.

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

Type Parameters

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.

Parameters

source
IEnumerable<TSource>

IEnumerable<T> a partir del cual se va a crear Lookup<TKey,TElement>.The IEnumerable<T> to create a Lookup<TKey,TElement> from.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de cada elemento.A function to extract a key from each element.

Returns

ILookup<TKey,TSource>

Lookup<TKey,TElement> que contiene claves y valores.A Lookup<TKey,TElement> that contains keys and values. Los valores de cada grupo están en el mismo orden que en source.The values within each group are in the same order as in source.

Exceptions

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

Remarks

El método ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) devuelve un Lookup<TKey,TElement>, un diccionario uno a varios que asigna claves a colecciones de valores.The ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Un Lookup<TKey,TElement> difiere de un Dictionary<TKey,TValue>, que realiza una asignación uno a uno de claves a valores únicos.A Lookup<TKey,TElement> differs from a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

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

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

Crea un objeto Lookup<TKey,TElement> a partir de un objeto IEnumerable<T> según una función del selector de claves especificada y el comparador de claves.Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.

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

Type Parameters

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.

Parameters

source
IEnumerable<TSource>

IEnumerable<T> a partir del cual se va a crear Lookup<TKey,TElement>.The IEnumerable<T> to create a Lookup<TKey,TElement> from.

keySelector
Func<TSource,TKey>

Función para extraer una clave a partir de cada elemento.A function to extract a key from each element.

comparer
IEqualityComparer<TKey>

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

Returns

ILookup<TKey,TSource>

Lookup<TKey,TElement> que contiene claves y valores.A Lookup<TKey,TElement> that contains keys and values. Los valores de cada grupo están en el mismo orden que en source.The values within each group are in the same order as in source.

Exceptions

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

Remarks

El método ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) devuelve un Lookup<TKey,TElement>, un diccionario uno a varios que asigna claves a colecciones de valores.The ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) method returns a Lookup<TKey,TElement>, a one-to-many dictionary that maps keys to collections of values. Una Lookup<TKey,TElement> es diferente a una Dictionary<TKey,TValue>, que realiza una asignación uno a uno de claves a valores únicos.A Lookup<TKey,TElement> is different to a Dictionary<TKey,TValue>, which performs a one-to-one mapping of keys to single values.

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

Applies to