Queryable.Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) 方法

定义

连接两个序列。Concatenates two sequences.

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IQueryable<TSource> ^ Concat(System::Linq::IQueryable<TSource> ^ source1, System::Collections::Generic::IEnumerable<TSource> ^ source2);
public static System.Linq.IQueryable<TSource> Concat<TSource> (this System.Linq.IQueryable<TSource> source1, System.Collections.Generic.IEnumerable<TSource> source2);
static member Concat : System.Linq.IQueryable<'Source> * seq<'Source> -> System.Linq.IQueryable<'Source>
<Extension()>
Public Function Concat(Of TSource) (source1 As IQueryable(Of TSource), source2 As IEnumerable(Of TSource)) As IQueryable(Of TSource)

类型参数

TSource

输入序列中的元素的类型。The type of the elements of the input sequences.

参数

source1
IQueryable<TSource>

要连接的第一个序列。The first sequence to concatenate.

source2
IEnumerable<TSource>

要与第一个序列连接的序列。The sequence to concatenate to the first sequence.

返回

IQueryable<TSource>

一个包含两个输入序列的连接元素的 IQueryable<T>An IQueryable<T> that contains the concatenated elements of the two input sequences.

例外

source1source2nullsource1 or source2 is null.

示例

下面的代码示例演示如何使用 Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) 来连接两个序列。The following code example demonstrates how to use Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) to concatenate two sequences.

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

// This method creates and returns an array of Pet objects.
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;
}

// This method creates and returns an array of Pet objects.
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();

    // Concatenate a collection of cat names to a
    // collection of dog names by using Concat().
    IEnumerable<string> query =
        cats.AsQueryable()
        .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


' This method creates and returns an array of Pet objects.
Shared 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

' This method creates and returns an array of Pet objects.
Shared 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

Shared Sub ConcatEx1()
    Dim cats() As Pet = GetCats()
    Dim dogs() As Pet = GetDogs()

    ' Concatenate a collection of cat names to a
    ' collection of dog names by using Concat().
    Dim query As IEnumerable(Of String) = _
        cats.AsQueryable() _
        .Select(Function(cat) cat.Name) _
        .Concat(dogs.Select(Function(dog) dog.Name))

    For Each name As String In query
        MsgBox(name)
    Next
End Sub

Structure Pet
    Dim Name As String
    Dim Age As Integer
End Structure

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

注解

Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) 方法生成一个 MethodCallExpression,它表示作为构造的泛型方法调用 Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) 本身。The Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) method generates a MethodCallExpression that represents calling Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) itself as a constructed generic method. 然后,它将 MethodCallExpression 传递到 IQueryProviderCreateQuery<TElement>(Expression) 方法(由 source1 参数的 Provider 属性表示)。It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source1 parameter.

因执行表示调用 Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) 的表达式树而发生的查询行为取决于 source1 参数类型的实现。The query behavior that occurs as a result of executing an expression tree that represents calling Concat<TSource>(IQueryable<TSource>, IEnumerable<TSource>) depends on the implementation of the type of the source1 parameter. 预期的行为是 source2 中的元素连接到 source1 的元素以创建新序列。The expected behavior is that the elements in source2 are concatenated to those of source1 to create a new sequence.

适用于