Enumerable.Concat(IEnumerable<TSource>, IEnumerable<TSource>) Enumerable.Concat(IEnumerable<TSource>, IEnumerable<TSource>) Enumerable.Concat(IEnumerable<TSource>, IEnumerable<TSource>) Enumerable.Concat(IEnumerable<TSource>, IEnumerable<TSource>) Method

定義

串連兩個序列。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)

類型參數

TSource

輸入序列之項目的類型。The type of the elements of the input sequences.

參數

first
IEnumerable<TSource>

要串連的第一個序列。The first sequence to concatenate.

second
IEnumerable<TSource>

要串連到第一個序列的序列。The sequence to concatenate to the first sequence.

傳回

IEnumerable<TSource>

IEnumerable<T> ,其中包含兩個輸入序列的串連項目。An IEnumerable<T> that contains the concatenated elements of the two input sequences.

例外狀況

firstsecondnullfirst or second is null.

範例

下列程式碼範例示範如何使用Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)來串連兩個序列。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.
    MsgBox(output.ToString())
End Sub

' This code produces the following output:
'
' Barley
' Boots
' Whiskers
' Bounder
' Snoopy
' Fido

串連兩個序列的替代方式是建構一個集合,例如陣列的序列,然後套用SelectMany方法,將身分識別選取器函式傳遞給它。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. 下列範例示範這個用法SelectManyThe 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.
    MsgBox(output.ToString())

    ' This code produces the following output:
    '
    ' Barley
    ' Boots
    ' Whiskers
    ' Bounder
    ' Snoopy
    ' Fido

備註

實作這個方法是使用延後的執行。This method is implemented by using deferred execution. 立即傳回值是儲存,才能執行此動作的所有資訊的物件。The immediate return value is an object that stores all the information that is required to perform the action. 這個方法所表示的查詢不會執行直到列舉物件可以藉由呼叫其GetEnumerator方法直接或透過foreachVisual C# 中或For EachVisual Basic 中。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.

Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)方法不同於Union方法因為Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)方法會傳回輸入序列中的所有原始的項目。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. Union方法會傳回唯一的項目。The Union method returns only unique elements.

適用於