Enumerable.Join Enumerable.Join Enumerable.Join Enumerable.Join Method

定義

根據相符索引鍵,將兩個序列的項目相互關聯。Correlates the elements of two sequences based on matching keys.

多載

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)

根據相符索引鍵,將兩個序列的項目相互關聯。Correlates the elements of two sequences based on matching keys. 預設的相等比較子是用於比較索引鍵。The default equality comparer is used to compare keys.

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)

根據相符索引鍵,將兩個序列的項目相互關聯。Correlates the elements of two sequences based on matching keys. 指定的 IEqualityComparer<T> 是用於比較索引鍵。A specified IEqualityComparer<T> is used to compare keys.

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)

根據相符索引鍵,將兩個序列的項目相互關聯。Correlates the elements of two sequences based on matching keys. 預設的相等比較子是用於比較索引鍵。The default equality comparer is used to compare keys.

public:
generic <typename TOuter, typename TInner, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ Join(System::Collections::Generic::IEnumerable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, Func<TOuter, TKey> ^ outerKeySelector, Func<TInner, TKey> ^ innerKeySelector, Func<TOuter, TInner, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> Join<TOuter,TInner,TKey,TResult> (this System.Collections.Generic.IEnumerable<TOuter> outer, System.Collections.Generic.IEnumerable<TInner> inner, Func<TOuter,TKey> outerKeySelector, Func<TInner,TKey> innerKeySelector, Func<TOuter,TInner,TResult> resultSelector);
static member Join : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> -> seq<'Result>
<Extension()>
Public Function Join(Of TOuter, TInner, TKey, TResult) (outer As IEnumerable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Func(Of TOuter, TKey), innerKeySelector As Func(Of TInner, TKey), resultSelector As Func(Of TOuter, TInner, TResult)) As IEnumerable(Of TResult)

類型參數

TOuter

第一個序列之項目的類型。The type of the elements of the first sequence.

TInner

第二個序列之項目的類型。The type of the elements of the second sequence.

TKey

索引鍵選取器函式所傳回之索引鍵的類型。The type of the keys returned by the key selector functions.

TResult

結果項目的類型。The type of the result elements.

參數

outer
IEnumerable<TOuter>

要聯結的第一個序列。The first sequence to join.

inner
IEnumerable<TInner>

要加入第一個序列的序列。The sequence to join to the first sequence.

outerKeySelector
Func<TOuter,TKey>

用來從第一個序列各個項目擷取聯結索引鍵的函式。A function to extract the join key from each element of the first sequence.

innerKeySelector
Func<TInner,TKey>

用來從第二個序列各個項目擷取聯結索引鍵的函式。A function to extract the join key from each element of the second sequence.

resultSelector
Func<TOuter,TInner,TResult>

用來從兩個相符項目建立結果項目的函式。A function to create a result element from two matching elements.

傳回

IEnumerable<TResult>

IEnumerable<T>,其中包含透過對兩個序列執行內部聯結所取得之型別 TResult 的項目。An IEnumerable<T> that has elements of type TResult that are obtained by performing an inner join on two sequences.

例外狀況

outerinnerouterKeySelectorinnerKeySelectorresultSelectornullouter or inner or outerKeySelector or innerKeySelector or resultSelector is null.

範例

下列程式碼範例示範如何使用Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) , 根據一般索引鍵來執行兩個序列的內部聯結。The following code example demonstrates how to use Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) to perform an inner join of two sequences based on a common key.

class Person
{
    public string Name { get; set; }
}

class Pet
{
    public string Name { get; set; }
    public Person Owner { get; set; }
}

public static void JoinEx1()
{
    Person magnus = new Person { Name = "Hedlund, Magnus" };
    Person terry = new Person { Name = "Adams, Terry" };
    Person charlotte = new Person { Name = "Weiss, Charlotte" };

    Pet barley = new Pet { Name = "Barley", Owner = terry };
    Pet boots = new Pet { Name = "Boots", Owner = terry };
    Pet whiskers = new Pet { Name = "Whiskers", Owner = charlotte };
    Pet daisy = new Pet { Name = "Daisy", Owner = magnus };

    List<Person> people = new List<Person> { magnus, terry, charlotte };
    List<Pet> pets = new List<Pet> { barley, boots, whiskers, daisy };

    // Create a list of Person-Pet pairs where 
    // each element is an anonymous type that contains a
    // Pet's name and the name of the Person that owns the Pet.
    var query =
        people.Join(pets,
                    person => person,
                    pet => pet.Owner,
                    (person, pet) =>
                        new { OwnerName = person.Name, Pet = pet.Name });

    foreach (var obj in query)
    {
        Console.WriteLine(
            "{0} - {1}",
            obj.OwnerName,
            obj.Pet);
    }
}

/*
 This code produces the following output:

 Hedlund, Magnus - Daisy
 Adams, Terry - Barley
 Adams, Terry - Boots
 Weiss, Charlotte - Whiskers
*/
Structure Person
    Public Name As String
End Structure

Structure Pet
    Public Name As String
    Public Owner As Person
End Structure

Sub JoinEx1()
    Dim magnus As New Person With {.Name = "Hedlund, Magnus"}
    Dim terry As New Person With {.Name = "Adams, Terry"}
    Dim charlotte As New Person With {.Name = "Weiss, Charlotte"}

    Dim barley As New Pet With {.Name = "Barley", .Owner = terry}
    Dim boots As New Pet With {.Name = "Boots", .Owner = terry}
    Dim whiskers As New Pet With {.Name = "Whiskers", .Owner = charlotte}
    Dim daisy As New Pet With {.Name = "Daisy", .Owner = magnus}

    Dim people As New List(Of Person)(New Person() {magnus, terry, charlotte})
    Dim pets As New List(Of Pet)(New Pet() {barley, boots, whiskers, daisy})

    ' Create a list of Person-Pet pairs, where each element is an
    ' anonymous type that contains a Pet's name and the name of the 
    ' Person that owns the Pet.
    Dim query =
people.Join(pets,
            Function(person) person,
            Function(pet) pet.Owner,
            Function(person, pet) _
                New With {.OwnerName = person.Name, .Pet = pet.Name})

    Dim output As New System.Text.StringBuilder
    For Each obj In query
        output.AppendLine(obj.OwnerName & " - " & obj.Pet)
    Next

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

' This code produces the following output:
'
' Hedlund, Magnus - Daisy
' Adams, Terry - Barley
' Adams, Terry - Boots
' Weiss, Charlotte - Whiskers

備註

這個方法是使用延後執行來執行。This method is implemented by using deferred execution. 立即傳回值是一個物件, 它會儲存執行動作所需的所有資訊。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, 必須等到透過直接GetEnumerator呼叫其方法, 或是在 Visual C#或For Each Visual Basic 中使用foreach來列舉物件之後, 才會執行。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.

預設的相等比較Default子是用來雜湊和比較索引鍵。The default equality comparer, Default, is used to hash and compare keys.

聯結是指根據一般索引鍵, 將兩個資訊來源的元素相互關聯的作業。A join refers to the operation of correlating the elements of two sources of information based on a common key. Join將兩個資訊來源和用來比對的索引鍵放在一個方法呼叫中。Join brings the two information sources and the keys by which they are matched together in one method call. 這與使用SelectMany不同, 因為它需要一個以上的方法呼叫來執行相同的作業。This differs from the use of SelectMany, which requires more than one method call to perform the same operation.

Join會保留專案的outer順序, 並針對每個專案, 為的相符inner元素順序。Join preserves the order of the elements of outer, and for each of these elements, the order of the matching elements of inner.

在查詢運算式語法中, join (Visual C#) 或Join (Visual Basic) 子句會轉譯成的Join調用。In query expression syntax, a join (Visual C#) or Join (Visual Basic) clause translates to an invocation of Join.

在關係資料庫詞彙中, Join方法會實作為內部等聯結。In relational database terms, the Join method implements an inner equijoin. 「內部」表示只有在另一個序列中具有相符專案的元素才會包含在結果中。'Inner' means that only elements that have a match in the other sequence are included in the results. 「對等聯結」是用來比較索引鍵是否相等的聯結。An 'equijoin' is a join in which the keys are compared for equality. 左方外部聯結作業沒有專用的GroupJoin標準查詢運算子, 但可以使用方法來執行。A left outer join operation has no dedicated standard query operator, but can be performed by using the GroupJoin method. 請參閱聯結作業See Join Operations.

另請參閱

Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>) Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)

根據相符索引鍵,將兩個序列的項目相互關聯。Correlates the elements of two sequences based on matching keys. 指定的 IEqualityComparer<T> 是用於比較索引鍵。A specified IEqualityComparer<T> is used to compare keys.

public:
generic <typename TOuter, typename TInner, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ Join(System::Collections::Generic::IEnumerable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, Func<TOuter, TKey> ^ outerKeySelector, Func<TInner, TKey> ^ innerKeySelector, Func<TOuter, TInner, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> Join<TOuter,TInner,TKey,TResult> (this System.Collections.Generic.IEnumerable<TOuter> outer, System.Collections.Generic.IEnumerable<TInner> inner, Func<TOuter,TKey> outerKeySelector, Func<TInner,TKey> innerKeySelector, Func<TOuter,TInner,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member Join : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function Join(Of TOuter, TInner, TKey, TResult) (outer As IEnumerable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Func(Of TOuter, TKey), innerKeySelector As Func(Of TInner, TKey), resultSelector As Func(Of TOuter, TInner, TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

類型參數

TOuter

第一個序列之項目的類型。The type of the elements of the first sequence.

TInner

第二個序列之項目的類型。The type of the elements of the second sequence.

TKey

索引鍵選取器函式所傳回之索引鍵的類型。The type of the keys returned by the key selector functions.

TResult

結果項目的類型。The type of the result elements.

參數

outer
IEnumerable<TOuter>

要聯結的第一個序列。The first sequence to join.

inner
IEnumerable<TInner>

要加入第一個序列的序列。The sequence to join to the first sequence.

outerKeySelector
Func<TOuter,TKey>

用來從第一個序列各個項目擷取聯結索引鍵的函式。A function to extract the join key from each element of the first sequence.

innerKeySelector
Func<TInner,TKey>

用來從第二個序列各個項目擷取聯結索引鍵的函式。A function to extract the join key from each element of the second sequence.

resultSelector
Func<TOuter,TInner,TResult>

用來從兩個相符項目建立結果項目的函式。A function to create a result element from two matching elements.

comparer
IEqualityComparer<TKey>

用來雜湊及比較索引鍵的 IEqualityComparer<T>An IEqualityComparer<T> to hash and compare keys.

傳回

IEnumerable<TResult>

IEnumerable<T>,其中包含透過對兩個序列執行內部聯結所取得之型別 TResult 的項目。An IEnumerable<T> that has elements of type TResult that are obtained by performing an inner join on two sequences.

例外狀況

outerinnerouterKeySelectorinnerKeySelectorresultSelectornullouter or inner or outerKeySelector or innerKeySelector or resultSelector is null.

備註

這個方法是使用延後執行來執行。This method is implemented by using deferred execution. 立即傳回值是一個物件, 它會儲存執行動作所需的所有資訊。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, 必須等到透過直接GetEnumerator呼叫其方法, 或是在 Visual C#或For Each Visual Basic 中使用foreach來列舉物件之後, 才會執行。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.

如果comparer Defaultnull, 則會使用預設的相等比較子來雜湊和比較索引鍵。If comparer is null, the default equality comparer, Default, is used to hash and compare keys.

聯結是指根據一般索引鍵, 將兩個資訊來源的元素相互關聯的作業。A join refers to the operation of correlating the elements of two sources of information based on a common key. Join將兩個資訊來源和用來比對的索引鍵放在一個方法呼叫中。Join brings the two information sources and the keys by which they are matched together in one method call. 這與使用SelectMany不同, 因為它需要一個以上的方法呼叫來執行相同的作業。This differs from the use of SelectMany, which requires more than one method call to perform the same operation.

Join會保留專案的outer順序, 並針對每個專案, 為的相符inner元素順序。Join preserves the order of the elements of outer, and for each of these elements, the order of the matching elements of inner.

在關係資料庫詞彙中, Join方法會實作為內部等聯結。In relational database terms, the Join method implements an inner equijoin. 「內部」表示只有在另一個序列中具有相符專案的元素才會包含在結果中。'Inner' means that only elements that have a match in the other sequence are included in the results. 「對等聯結」是用來比較索引鍵是否相等的聯結。An 'equijoin' is a join in which the keys are compared for equality. 左方外部聯結作業沒有專用的GroupJoin標準查詢運算子, 但可以使用方法來執行。A left outer join operation has no dedicated standard query operator, but can be performed by using the GroupJoin method. 請參閱聯結作業See Join Operations.

另請參閱

適用於