Enumerable.Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) Metodo
Definizione
Concatena due sequenze.Concatenates two sequences.
public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
static System::Collections::Generic::IEnumerable<TSource> ^ Concat(System::Collections::Generic::IEnumerable<TSource> ^ first, System::Collections::Generic::IEnumerable<TSource> ^ second);
public static System.Collections.Generic.IEnumerable<TSource> Concat<TSource> (this System.Collections.Generic.IEnumerable<TSource> first, System.Collections.Generic.IEnumerable<TSource> second);
static member Concat : seq<'Source> * seq<'Source> -> seq<'Source>
<Extension()>
Public Function Concat(Of TSource) (first As IEnumerable(Of TSource), second As IEnumerable(Of TSource)) As IEnumerable(Of TSource)
Parametri di tipo
- TSource
Tipo degli elementi delle sequenze di input.The type of the elements of the input sequences.
Parametri
- first
- IEnumerable<TSource>
Prima sequenza da concatenare.The first sequence to concatenate.
- second
- IEnumerable<TSource>
Sequenza da concatenare alla prima sequenza.The sequence to concatenate to the first sequence.
Restituisce
- IEnumerable<TSource>
Un oggetto IEnumerable<T> che contiene gli elementi concatenati delle due sequenze di input.An IEnumerable<T> that contains the concatenated elements of the two input sequences.
Eccezioni
first
o second
è null
.first
or second
is null
.
Esempio
Nell'esempio di codice riportato di seguito viene illustrato come utilizzare Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) per concatenare due sequenze.The following code example demonstrates how to use Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) to concatenate two sequences.
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
static Pet[] GetCats()
{
Pet[] cats = { new Pet { Name="Barley", Age=8 },
new Pet { Name="Boots", Age=4 },
new Pet { Name="Whiskers", Age=1 } };
return cats;
}
static Pet[] GetDogs()
{
Pet[] dogs = { new Pet { Name="Bounder", Age=3 },
new Pet { Name="Snoopy", Age=14 },
new Pet { Name="Fido", Age=9 } };
return dogs;
}
public static void ConcatEx1()
{
Pet[] cats = GetCats();
Pet[] dogs = GetDogs();
IEnumerable<string> query =
cats.Select(cat => cat.Name).Concat(dogs.Select(dog => dog.Name));
foreach (string name in query)
{
Console.WriteLine(name);
}
}
// This code produces the following output:
//
// Barley
// Boots
// Whiskers
// Bounder
// Snoopy
// Fido
Structure Pet
Public Name As String
Public Age As Integer
End Structure
' Returns an array of Pet objects.
Function GetCats() As Pet()
Dim cats() As Pet = {New Pet With {.Name = "Barley", .Age = 8},
New Pet With {.Name = "Boots", .Age = 4},
New Pet With {.Name = "Whiskers", .Age = 1}}
Return cats
End Function
' Returns an array of Pet objects.
Function GetDogs() As Pet()
Dim dogs() As Pet = {New Pet With {.Name = "Bounder", .Age = 3},
New Pet With {.Name = "Snoopy", .Age = 14},
New Pet With {.Name = "Fido", .Age = 9}}
Return dogs
End Function
Sub ConcatEx1()
' Create two arrays of Pet objects.
Dim cats() As Pet = GetCats()
Dim dogs() As Pet = GetDogs()
' Project the Name of each cat and concatenate
' the collection of cat name strings with a collection
' of dog name strings.
Dim query As IEnumerable(Of String) =
cats _
.Select(Function(cat) cat.Name) _
.Concat(dogs.Select(Function(dog) dog.Name))
Dim output As New System.Text.StringBuilder
For Each name As String In query
output.AppendLine(name)
Next
' Display the output.
Console.WriteLine(output.ToString())
End Sub
' This code produces the following output:
'
' Barley
' Boots
' Whiskers
' Bounder
' Snoopy
' Fido
Un modo alternativo per concatenare due sequenze è costruire una raccolta, ad esempio una matrice, di sequenze e quindi applicare il SelectMany metodo, passandogli la funzione del selettore di identità.An alternative way of concatenating two sequences is to construct a collection, for example an array, of sequences and then apply the SelectMany method, passing it the identity selector function. Nell'esempio seguente viene illustrato l'utilizzo di SelectMany .The following example demonstrates this use of SelectMany.
Pet[] cats = GetCats();
Pet[] dogs = GetDogs();
IEnumerable<string> query =
new[] { cats.Select(cat => cat.Name), dogs.Select(dog => dog.Name) }
.SelectMany(name => name);
foreach (string name in query)
{
Console.WriteLine(name);
}
// This code produces the following output:
//
// Barley
// Boots
// Whiskers
// Bounder
// Snoopy
// Fido
' Create two arrays of Pet objects.
Dim cats() As Pet = GetCats()
Dim dogs() As Pet = GetDogs()
' Create an IEnumerable collection that contains two elements.
' Each element is an array of Pet objects.
Dim animals() As IEnumerable(Of Pet) = {cats, dogs}
Dim query As IEnumerable(Of String) =
(animals.SelectMany(Function(pets) _
pets.Select(Function(pet) pet.Name)))
Dim output As New System.Text.StringBuilder
For Each name As String In query
output.AppendLine(name)
Next
' Display the output.
Console.WriteLine(output.ToString())
' This code produces the following output:
'
' Barley
' Boots
' Whiskers
' Bounder
' Snoopy
' Fido
Commenti
Questo metodo viene implementato tramite l'esecuzione posticipata.This method is implemented by using deferred execution. Il valore restituito immediato 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 finché l'oggetto non viene enumerato chiamando il relativo GetEnumerator
metodo direttamente o utilizzando 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 metodo è Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) diverso dal Union metodo perché il Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) metodo restituisce tutti gli elementi originali nelle sequenze di input.The Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method differs from the Union method because the Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>) method returns all the original elements in the input sequences. Il Union metodo restituisce solo elementi univoci.The Union method returns only unique elements.