Enumerable.SelectMany Enumerable.SelectMany Enumerable.SelectMany Enumerable.SelectMany Method

Definizione

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T> e semplifica le sequenze risultanti in un’unica sequenza.Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.

Overload

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T>, semplifica le sequenze risultanti in un'unica sequenza e richiama una funzione del selettore di risultato su ogni elemento al suo interno.Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T>, semplifica le sequenze risultanti in un'unica sequenza e richiama una funzione del selettore di risultato su ogni elemento al suo interno.Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. L'indice di ogni elemento di origine viene usato nella maschera intermedia proiettata di tale elemento.The index of each source element is used in the intermediate projected form of that element.

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T> e semplifica le sequenze risultanti in un’unica sequenza.Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T> e semplifica le sequenze risultanti in un’unica sequenza.Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. L'indice di ogni elemento di origine viene usato nella maschera proiettata di tale elemento.The index of each source element is used in the projected form of that element.

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T>, semplifica le sequenze risultanti in un'unica sequenza e richiama una funzione del selettore di risultato su ogni elemento al suo interno.Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.

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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TCollection

Tipo degli elementi intermedi raccolti da collectionSelector.The type of the intermediate elements collected by collectionSelector.

TResult

Tipo degli elementi della sequenza risultante.The type of the elements of the resulting sequence.

Parametri

source
IEnumerable<TSource>

Sequenza di valori da proiettare.A sequence of values to project.

collectionSelector
Func<TSource,IEnumerable<TCollection>>

Funzione di trasformazione da applicare a ogni elemento della sequenza di input.A transform function to apply to each element of the input sequence.

resultSelector
Func<TSource,TCollection,TResult>

Funzione di trasformazione da applicare a ogni elemento della sequenza intermedia.A transform function to apply to each element of the intermediate sequence.

Restituisce

IEnumerable<TResult>

Oggetto IEnumerable<T> i cui elementi sono il risultato ottenuto richiamando la funzione di trasformazione uno a molti collectionSelector su ogni elemento di source ed eseguire quindi il mapping di ognuno degli elementi di tale sequenza e del corrispondente elemento di origine a un elemento di risultato.An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function collectionSelector on each element of source and then mapping each of those sequence elements and their corresponding source element to a result element.

Eccezioni

Il parametro source, il parametro collectionSelector o il parametro resultSelector è null.source or collectionSelector or resultSelector is null.

Esempi

Esempio di codice seguente viene illustrato come utilizzare SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) per eseguire una proiezione di uno-a-molti su una matrice e usare una funzione del selettore di risultato per mantenere ogni elemento corrispondente dalla sequenza di origine nell'ambito per la chiamata finale al Select.The following code example demonstrates how to use SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) to perform a one-to-many projection over an array and use a result selector function to keep each corresponding element from the source sequence in scope for the final call to Select.

class PetOwner
{
    public string Name { get; set; }
    public List<string> Pets { get; set; }
}

public static void SelectManyEx3()
{
    PetOwner[] petOwners =
        { new PetOwner { Name="Higa", 
              Pets = new List<string>{ "Scruffy", "Sam" } },
          new PetOwner { Name="Ashkenazi", 
              Pets = new List<string>{ "Walker", "Sugar" } },
          new PetOwner { Name="Price", 
              Pets = new List<string>{ "Scratches", "Diesel" } },
          new PetOwner { Name="Hines", 
              Pets = new List<string>{ "Dusty" } } };

    // Project the pet owner's name and the pet's name.
    var query =
        petOwners
        .SelectMany(petOwner => petOwner.Pets, (petOwner, petName) => new { petOwner, petName })
        .Where(ownerAndPet => ownerAndPet.petName.StartsWith("S"))
        .Select(ownerAndPet =>
                new
                {
                    Owner = ownerAndPet.petOwner.Name,
                    Pet = ownerAndPet.petName
                }
        );

    // Print the results.
    foreach (var obj in query)
    {
        Console.WriteLine(obj);
    }
}

// This code produces the following output:
//
// {Owner=Higa, Pet=Scruffy}
// {Owner=Higa, Pet=Sam}
// {Owner=Ashkenazi, Pet=Sugar}
// {Owner=Price, Pet=Scratches}
Structure PetOwner
    Public Name As String
    Public Pets() As String
End Structure

Sub SelectManyEx3()
    ' Create an array of PetOwner objects.
    Dim petOwners() As PetOwner =
{New PetOwner With
 {.Name = "Higa", .Pets = New String() {"Scruffy", "Sam"}},
 New PetOwner With
 {.Name = "Ashkenazi", .Pets = New String() {"Walker", "Sugar"}},
 New PetOwner With
 {.Name = "Price", .Pets = New String() {"Scratches", "Diesel"}},
 New PetOwner With
 {.Name = "Hines", .Pets = New String() {"Dusty"}}}

    ' Project an anonymous type that consists of
    ' the owner's name and the pet's name (string).
    Dim query =
petOwners _
.SelectMany(
    Function(petOwner) petOwner.Pets,
    Function(petOwner, petName) New With {petOwner, petName}) _
.Where(Function(ownerAndPet) ownerAndPet.petName.StartsWith("S")) _
.Select(Function(ownerAndPet) _
       New With {.Owner = ownerAndPet.petOwner.Name,
                 .Pet = ownerAndPet.petName
       })

    Dim output As New System.Text.StringBuilder
    For Each obj In query
        output.AppendLine(String.Format("Owner={0}, Pet={1}", obj.Owner, obj.Pet))
    Next

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

' This code produces the following output:
'
' Owner=Higa, Pet=Scruffy
' Owner=Higa, Pet=Sam
' Owner=Ashkenazi, Pet=Sugar
' Owner=Price, Pet=Scratches

Commenti

Questo metodo viene implementato tramite l'esecuzione posticipata.This method is implemented by using deferred execution. Il controllo immediato valore restituito è un oggetto che archivia tutte le informazioni necessarie per eseguire l'azione.The immediate return value is an object that stores all the information that is required to perform the action. La query rappresentata da questo metodo non viene eseguita fino a quando l'oggetto viene enumerata chiamando relativi GetEnumerator metodo direttamente o tramite foreach in Visual c# o For Each in 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.

Il SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) metodo è utile quando è necessario tenere gli elementi della source nell'ambito per la logica di query che si verifica dopo la chiamata a SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>).The SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) method is useful when you have to keep the elements of source in scope for query logic that occurs after the call to SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>). Per un esempio di codice, vedere la sezione relativa agli esempi.See the Example section for a code example. Se è presente una relazione bidirezionale tra gli oggetti di tipo TSource e gli oggetti di tipo TCollection, vale a dire, se un oggetto di tipo TCollection fornisce una proprietà per recuperare il TSource oggetto che ha generato, non è necessario questo eseguire l'overload di SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>).If there is a bidirectional relationship between objects of type TSource and objects of type TCollection, that is, if an object of type TCollection provides a property to retrieve the TSource object that produced it, you do not need this overload of SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>). In alternativa, è possibile usare SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) e tornare al TSource dell'oggetto tramite il TCollection oggetto.Instead, you can use SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) and navigate back to the TSource object through the TCollection object.

Nella sintassi delle espressioni di query, ciascuna from clausola (Visual c#) o From clausola (Visual Basic) dopo l'iniziale, viene convertita in una chiamata di SelectMany.In query expression syntax, each from clause (Visual C#) or From clause (Visual Basic) after the initial one translates to an invocation of SelectMany.

Vedi anche

SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T>, semplifica le sequenze risultanti in un'unica sequenza e richiama una funzione del selettore di risultato su ogni elemento al suo interno.Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. L'indice di ogni elemento di origine viene usato nella maschera intermedia proiettata di tale elemento.The index of each source element is used in the intermediate projected form of that element.

public:
generic <typename TSource, typename TCollection, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ SelectMany(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, int, System::Collections::Generic::IEnumerable<TCollection> ^> ^ collectionSelector, Func<TSource, TCollection, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> SelectMany<TSource,TCollection,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,int,System.Collections.Generic.IEnumerable<TCollection>> collectionSelector, Func<TSource,TCollection,TResult> resultSelector);
static member SelectMany : seq<'Source> * Func<'Source, int, seq<'Collection>> * Func<'Source, 'Collection, 'Result> -> seq<'Result>
<Extension()>
Public Function SelectMany(Of TSource, TCollection, TResult) (source As IEnumerable(Of TSource), collectionSelector As Func(Of TSource, Integer, IEnumerable(Of TCollection)), resultSelector As Func(Of TSource, TCollection, TResult)) As IEnumerable(Of TResult)

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TCollection

Tipo degli elementi intermedi raccolti da collectionSelector.The type of the intermediate elements collected by collectionSelector.

TResult

Tipo degli elementi della sequenza risultante.The type of the elements of the resulting sequence.

Parametri

source
IEnumerable<TSource>

Sequenza di valori da proiettare.A sequence of values to project.

collectionSelector
Func<TSource,Int32,IEnumerable<TCollection>>

Funzione di trasformazione da applicare a ogni elemento di origine; il secondo parametro della funzione rappresenta l'indice dell'elemento di origine.A transform function to apply to each source element; the second parameter of the function represents the index of the source element.

resultSelector
Func<TSource,TCollection,TResult>

Funzione di trasformazione da applicare a ogni elemento della sequenza intermedia.A transform function to apply to each element of the intermediate sequence.

Restituisce

IEnumerable<TResult>

Oggetto IEnumerable<T> i cui elementi sono il risultato ottenuto richiamando la funzione di trasformazione uno a molti collectionSelector su ogni elemento di source ed eseguire quindi il mapping di ognuno degli elementi di tale sequenza e del corrispondente elemento di origine a un elemento di risultato.An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function collectionSelector on each element of source and then mapping each of those sequence elements and their corresponding source element to a result element.

Eccezioni

Il parametro source, il parametro collectionSelector o il parametro resultSelector è null.source or collectionSelector or resultSelector is null.

Commenti

Questo metodo viene implementato tramite l'esecuzione posticipata.This method is implemented by using deferred execution. Il controllo immediato valore restituito è un oggetto che archivia tutte le informazioni necessarie per eseguire l'azione.The immediate return value is an object that stores all the information that is required to perform the action. La query rappresentata da questo metodo non viene eseguita fino a quando l'oggetto viene enumerata chiamando relativi GetEnumerator metodo direttamente o tramite foreach in Visual c# o For Each in 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.

Il SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) metodo è utile quando è necessario tenere gli elementi della source nell'ambito per la logica di query che si verifica dopo la chiamata a SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>).The SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>) method is useful when you have to keep the elements of source in scope for query logic that occurs after the call to SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>). Per un esempio di codice, vedere la sezione relativa agli esempi.See the Example section for a code example. Se è presente una relazione bidirezionale tra gli oggetti di tipo TSource e gli oggetti di tipo TCollection, vale a dire, se un oggetto di tipo TCollection fornisce una proprietà per recuperare il TSource oggetto che ha generato, non è necessario questo eseguire l'overload di SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>).If there is a bidirectional relationship between objects of type TSource and objects of type TCollection, that is, if an object of type TCollection provides a property to retrieve the TSource object that produced it, you do not need this overload of SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>). In alternativa, è possibile usare SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) e tornare al TSource dell'oggetto tramite il TCollection oggetto.Instead, you can use SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) and navigate back to the TSource object through the TCollection object.

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T> e semplifica le sequenze risultanti in un’unica sequenza.Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.

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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TResult

Tipo degli elementi della sequenza restituita da selector.The type of the elements of the sequence returned by selector.

Parametri

source
IEnumerable<TSource>

Sequenza di valori da proiettare.A sequence of values to project.

selector
Func<TSource,IEnumerable<TResult>>

Funzione di trasformazione da applicare a ogni elemento.A transform function to apply to each element.

Restituisce

IEnumerable<TResult>

Oggetto IEnumerable<T> i cui elementi sono il risultato ottenuto richiamando la funzione di trasformazione uno a molti su ogni elemento della sequenza di input.An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function on each element of the input sequence.

Eccezioni

source o selector è null.source or selector is null.

Esempi

Esempio di codice seguente viene illustrato come utilizzare SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) per eseguire una proiezione di uno-a-molti su una matrice.The following code example demonstrates how to use SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) to perform a one-to-many projection over an array.

class PetOwner
{
    public string Name { get; set; }
    public List<String> Pets { get; set; }
}

public static void SelectManyEx1()
{
    PetOwner[] petOwners = 
        { new PetOwner { Name="Higa, Sidney", 
              Pets = new List<string>{ "Scruffy", "Sam" } },
          new PetOwner { Name="Ashkenazi, Ronen", 
              Pets = new List<string>{ "Walker", "Sugar" } },
          new PetOwner { Name="Price, Vernette", 
              Pets = new List<string>{ "Scratches", "Diesel" } } };

    // Query using SelectMany().
    IEnumerable<string> query1 = petOwners.SelectMany(petOwner => petOwner.Pets);

    Console.WriteLine("Using SelectMany():");

    // Only one foreach loop is required to iterate 
    // through the results since it is a
    // one-dimensional collection.
    foreach (string pet in query1)
    {
        Console.WriteLine(pet);
    }

    // This code shows how to use Select() 
    // instead of SelectMany().
    IEnumerable<List<String>> query2 =
        petOwners.Select(petOwner => petOwner.Pets);

    Console.WriteLine("\nUsing Select():");

    // Notice that two foreach loops are required to 
    // iterate through the results
    // because the query returns a collection of arrays.
    foreach (List<String> petList in query2)
    {
        foreach (string pet in petList)
        {
            Console.WriteLine(pet);
        }
        Console.WriteLine();
    }
}

/*
 This code produces the following output:

 Using SelectMany():
 Scruffy
 Sam
 Walker
 Sugar
 Scratches
 Diesel

 Using Select():
 Scruffy
 Sam

 Walker
 Sugar

 Scratches
 Diesel
*/
Structure PetOwner
    Public Name As String
    Public Pets() As String
End Structure

Sub SelectManyEx1()
    ' Create an array of PetOwner objects.
    Dim petOwners() As PetOwner =
{New PetOwner With
 {.Name = "Higa, Sidney", .Pets = New String() {"Scruffy", "Sam"}},
 New PetOwner With
 {.Name = "Ashkenazi, Ronen", .Pets = New String() {"Walker", "Sugar"}},
 New PetOwner With
 {.Name = "Price, Vernette", .Pets = New String() {"Scratches", "Diesel"}}}

    ' Call SelectMany() to gather all pets into a "flat" sequence.
    Dim query1 As IEnumerable(Of String) =
petOwners.SelectMany(Function(petOwner) petOwner.Pets)

    Dim output As New System.Text.StringBuilder("Using SelectMany():" & vbCrLf)
    ' Only one foreach loop is required to iterate through 
    ' the results because it is a one-dimensional collection.
    For Each pet As String In query1
        output.AppendLine(pet)
    Next

    ' This code demonstrates how to use Select() instead 
    ' of SelectMany() to get the same result.
    Dim query2 As IEnumerable(Of String()) =
petOwners.Select(Function(petOwner) petOwner.Pets)
    output.AppendLine(vbCrLf & "Using Select():")
    ' Notice that two foreach loops are required to iterate through 
    ' the results because the query returns a collection of arrays.
    For Each petArray() As String In query2
        For Each pet As String In petArray
            output.AppendLine(pet)
        Next
    Next

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

' This code produces the following output:
'
' Using SelectMany():
' Scruffy
' Sam
' Walker
' Sugar
' Scratches
' Diesel
'
' Using Select():
' Scruffy
' Sam
' Walker
' Sugar
' Scratches
' Diesel

Commenti

Questo metodo viene implementato tramite l'esecuzione posticipata.This method is implemented by using deferred execution. Il controllo immediato valore restituito è un oggetto che archivia tutte le informazioni necessarie per eseguire l'azione.The immediate return value is an object that stores all the information that is required to perform the action. La query rappresentata da questo metodo non viene eseguita fino a quando l'oggetto viene enumerata chiamando relativi GetEnumerator metodo direttamente o tramite foreach in Visual c# o For Each in 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.

Il SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) metodo enumera la sequenza di input, utilizza una funzione di trasformazione per eseguire il mapping di ogni elemento in un IEnumerable<T>e quindi enumera e restituisce gli elementi della ognuno di tali IEnumerable<T> oggetto.The SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) method enumerates the input sequence, uses a transform function to map each element to an IEnumerable<T>, and then enumerates and yields the elements of each such IEnumerable<T> object. Vale a dire, per ogni elemento della source, selector viene richiamato e viene restituita una sequenza di valori.That is, for each element of source, selector is invoked and a sequence of values is returned. SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) rende quindi flat questa raccolta bidimensionale di raccolte in una matrice unidimensionale IEnumerable<T> e lo restituisce.SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) then flattens this two-dimensional collection of collections into a one-dimensional IEnumerable<T> and returns it. Ad esempio, se una query viene utilizzata SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) per ottenere gli ordini (di tipo Order) per ogni cliente in un database, il risultato è di tipo IEnumerable<Order> in c# o IEnumerable(Of Order) in Visual Basic.For example, if a query uses SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>) to obtain the orders (of type Order) for each customer in a database, the result is of type IEnumerable<Order> in C# or IEnumerable(Of Order) in Visual Basic. Se invece la query utilizza Select per ottenere gli ordini, la raccolta di raccolte di ordini viene combinata non e il risultato è di tipo IEnumerable<List<Order>> in c# o IEnumerable(Of List(Of Order)) in Visual Basic.If instead the query uses Select to obtain the orders, the collection of collections of orders is not combined and the result is of type IEnumerable<List<Order>> in C# or IEnumerable(Of List(Of Order)) in Visual Basic.

Nella sintassi delle espressioni di query, ciascuna from clausola (Visual c#) o From clausola (Visual Basic) dopo l'iniziale, viene convertita in una chiamata di SelectMany.In query expression syntax, each from clause (Visual C#) or From clause (Visual Basic) after the initial one translates to an invocation of SelectMany.

Vedi anche

SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)

Proietta ogni elemento di una sequenza a un oggetto IEnumerable<T> e semplifica le sequenze risultanti in un’unica sequenza.Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. L'indice di ogni elemento di origine viene usato nella maschera proiettata di tale elemento.The index of each source element is used in the projected form of that element.

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

Parametri di tipo

TSource

Tipo degli elementi di source.The type of the elements of source.

TResult

Tipo degli elementi della sequenza restituita da selector.The type of the elements of the sequence returned by selector.

Parametri

source
IEnumerable<TSource>

Sequenza di valori da proiettare.A sequence of values to project.

selector
Func<TSource,Int32,IEnumerable<TResult>>

Funzione di trasformazione da applicare a ogni elemento di origine; il secondo parametro della funzione rappresenta l'indice dell'elemento di origine.A transform function to apply to each source element; the second parameter of the function represents the index of the source element.

Restituisce

IEnumerable<TResult>

Oggetto IEnumerable<T> i cui elementi sono il risultato ottenuto richiamando la funzione di trasformazione uno a molti su ogni elemento di una sequenza di input.An IEnumerable<T> whose elements are the result of invoking the one-to-many transform function on each element of an input sequence.

Eccezioni

source o selector è null.source or selector is null.

Esempi

Esempio di codice seguente viene illustrato come utilizzare SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) per eseguire una proiezione di uno-a-molti su una matrice e usare l'indice di ogni elemento esterno.The following code example demonstrates how to use SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) to perform a one-to-many projection over an array and use the index of each outer element.

class PetOwner
{
    public string Name { get; set; }
    public List<string> Pets { get; set; }
}

public static void SelectManyEx2()
{
    PetOwner[] petOwners = 
        { new PetOwner { Name="Higa, Sidney", 
              Pets = new List<string>{ "Scruffy", "Sam" } },
          new PetOwner { Name="Ashkenazi, Ronen", 
              Pets = new List<string>{ "Walker", "Sugar" } },
          new PetOwner { Name="Price, Vernette", 
              Pets = new List<string>{ "Scratches", "Diesel" } },
          new PetOwner { Name="Hines, Patrick", 
              Pets = new List<string>{ "Dusty" } } };

    // Project the items in the array by appending the index 
    // of each PetOwner to each pet's name in that petOwner's 
    // array of pets.
    IEnumerable<string> query =
        petOwners.SelectMany((petOwner, index) =>
                                 petOwner.Pets.Select(pet => index + pet));

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

// This code produces the following output:
//
// 0Scruffy
// 0Sam
// 1Walker
// 1Sugar
// 2Scratches
// 2Diesel
// 3Dusty
Structure PetOwner
    Public Name As String
    Public Pets() As String
End Structure

Sub SelectManyEx2()
    ' Create an array of PetOwner objects.
    Dim petOwners() As PetOwner =
{New PetOwner With
 {.Name = "Higa, Sidney", .Pets = New String() {"Scruffy", "Sam"}},
 New PetOwner With
 {.Name = "Ashkenazi, Ronen", .Pets = New String() {"Walker", "Sugar"}},
 New PetOwner With
 {.Name = "Price, Vernette", .Pets = New String() {"Scratches", "Diesel"}},
 New PetOwner With
 {.Name = "Hines, Patrick", .Pets = New String() {"Dusty"}}}

    ' Project the items in the array by appending the index 
    ' of each PetOwner to each pet's name in that petOwner's 
    ' array of pets.
    Dim query As IEnumerable(Of String) =
petOwners.SelectMany(Function(petOwner, index) _
                         petOwner.Pets.Select(Function(pet) _
                                                  index.ToString() + pet))

    Dim output As New System.Text.StringBuilder
    For Each pet As String In query
        output.AppendLine(pet)
    Next

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

Commenti

Questo metodo viene implementato tramite l'esecuzione posticipata.This method is implemented by using deferred execution. Il controllo immediato valore restituito è un oggetto che archivia tutte le informazioni necessarie per eseguire l'azione.The immediate return value is an object that stores all the information that is required to perform the action. La query rappresentata da questo metodo non viene eseguita fino a quando l'oggetto viene enumerata chiamando relativi GetEnumerator metodo direttamente o tramite foreach in Visual c# o For Each in 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.

Il SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) metodo enumera la sequenza di input, utilizza una funzione di trasformazione per eseguire il mapping di ogni elemento in un IEnumerable<T>e quindi enumera e restituisce gli elementi della ognuno di tali IEnumerable<T> oggetto.The SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) method enumerates the input sequence, uses a transform function to map each element to an IEnumerable<T>, and then enumerates and yields the elements of each such IEnumerable<T> object. Vale a dire, per ogni elemento della source, selector viene richiamato e viene restituita una sequenza di valori.That is, for each element of source, selector is invoked and a sequence of values is returned. SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) rende quindi flat questa raccolta bidimensionale di raccolte in una matrice unidimensionale IEnumerable<T> e lo restituisce.SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) then flattens this two-dimensional collection of collections into a one-dimensional IEnumerable<T> and returns it. Ad esempio, se una query viene utilizzata SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) per ottenere gli ordini (di tipo Order) per ogni cliente in un database, il risultato è di tipo IEnumerable<Order> in c# o IEnumerable(Of Order) in Visual Basic.For example, if a query uses SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>) to obtain the orders (of type Order) for each customer in a database, the result is of type IEnumerable<Order> in C# or IEnumerable(Of Order) in Visual Basic. Se invece la query utilizza Select per ottenere gli ordini, la raccolta di raccolte di ordini viene combinata non e il risultato è di tipo IEnumerable<List<Order>> in c# o IEnumerable(Of List(Of Order)) in Visual Basic.If instead the query uses Select to obtain the orders, the collection of collections of orders is not combined and the result is of type IEnumerable<List<Order>> in C# or IEnumerable(Of List(Of Order)) in Visual Basic.

Il primo argomento selector rappresenta l'elemento da elaborare.The first argument to selector represents the element to process. Il secondo argomento selector rappresenta l'indice in base zero dell'elemento nella sequenza di origine.The second argument to selector represents the zero-based index of that element in the source sequence. Ciò può essere utile se gli elementi sono in un ordine noto e si vuole eseguire un'operazione con un elemento in corrispondenza dell'indice specifico, ad esempio.This can be useful if the elements are in a known order and you want to do something with an element at a particular index, for example. Può anche essere utile se si desidera recuperare l'indice di uno o più elementi.It can also be useful if you want to retrieve the index of one or more elements.

Si applica a