Enumerable.GroupJoin 方法

定義

根據索引鍵相等與否,將兩個序列的項目相互關聯,並群組產生的結果。Correlates the elements of two sequences based on key equality, and groups the results.

多載

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

根據索引鍵相等與否,將兩個序列的項目相互關聯,並群組產生的結果。Correlates the elements of two sequences based on key equality and groups the results. 指定的 IEqualityComparer<T> 是用於比較索引鍵。A specified IEqualityComparer<T> is used to compare keys.

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

根據索引鍵相等與否,將兩個序列的項目相互關聯,並群組產生的結果。Correlates the elements of two sequences based on equality of keys and groups the results. 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.

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

根據索引鍵相等與否,將兩個序列的項目相互關聯,並群組產生的結果。Correlates the elements of two sequences based on key equality and groups the results. 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> ^ GroupJoin(System::Collections::Generic::IEnumerable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, Func<TOuter, TKey> ^ outerKeySelector, Func<TInner, TKey> ^ innerKeySelector, Func<TOuter, System::Collections::Generic::IEnumerable<TInner> ^, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupJoin<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,System.Collections.Generic.IEnumerable<TInner>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupJoin<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,System.Collections.Generic.IEnumerable<TInner>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);
static member GroupJoin : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, seq<'Inner>, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function GroupJoin(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, IEnumerable(Of 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,IEnumerable<TInner>,TResult>

函式,用來從第一個序列的項目以及第二個序列的相符項目集合建立結果項目。A function to create a result element from an element from the first sequence and a collection of matching elements from the second sequence.

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群組聯結所取得之型別 TResult 的項目。An IEnumerable<T> that contains elements of type TResult that are obtained by performing a grouped 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所執行。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不會執行,直到以 GetEnumerator foreach Visual c # 或 Visual Basic 中的方法來列舉物件為止 For EachThe 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 comparernull ,則會使用預設的相等比較子 Default 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.

GroupJoin 產生階層式結果,這表示的專案 outer 會與相符專案的集合配對 innerGroupJoin produces hierarchical results, which means that elements from outer are paired with collections of matching elements from inner. GroupJoin 可讓您根據的每個專案,以整個相符專案為基礎來建立結果 outerGroupJoin enables you to base your results on a whole set of matches for each element of outer.

注意

如果的指定專案中沒有相互關聯的專案 inner outer ,則該元素的相符序列將會是空的,但仍會出現在結果中。If there are no correlated elements in inner for a given element of outer, the sequence of matches for that element will be empty but will still appear in the results.

函式 resultSelector 只會針對每個專案呼叫一次, outer 並將所有 inner 符合該專案的元素集合 outerThe resultSelector function is called only one time for each outer element together with a collection of all the inner elements that match the outer element. 這不同于在 Join 包含一個專案的配對上叫用結果選取器函式, outer 以及一個元素 innerThis differs from the Join method in which the result selector function is invoked on pairs that contain one element from outer and one element from inner.

GroupJoin 保留的元素順序,以及的 outer 每個專案的順序 outer ,與相符元素的順序 innerGroupJoin preserves the order of the elements of outer, and for each element of outer, the order of the matching elements from inner.

GroupJoin 在傳統關係資料庫詞彙中沒有直接對等專案。GroupJoin has no direct equivalent in traditional relational database terms. 不過,這個方法會執行內部聯結和左方外部聯結的超集合。However, this method does implement a superset of inner joins and left outer joins. 這兩種作業都可以根據群組聯結來撰寫。Both of these operations can be written in terms of a grouped join. 請參閱 聯結作業See Join Operations.

另請參閱

適用於

產品 Introduced

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

根據索引鍵相等與否,將兩個序列的項目相互關聯,並群組產生的結果。Correlates the elements of two sequences based on equality of keys and groups the results. 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> ^ GroupJoin(System::Collections::Generic::IEnumerable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, Func<TOuter, TKey> ^ outerKeySelector, Func<TInner, TKey> ^ innerKeySelector, Func<TOuter, System::Collections::Generic::IEnumerable<TInner> ^, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> GroupJoin<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,System.Collections.Generic.IEnumerable<TInner>,TResult> resultSelector);
static member GroupJoin : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, seq<'Inner>, 'Result> -> seq<'Result>
<Extension()>
Public Function GroupJoin(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, IEnumerable(Of 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,IEnumerable<TInner>,TResult>

函式,用來從第一個序列的項目以及第二個序列的相符項目集合建立結果項目。A function to create a result element from an element from the first sequence and a collection of matching elements from the second sequence.

傳回

IEnumerable<TResult>

IEnumerable<T>,其中包含透過對兩個序列執行群組聯結所取得之型別 TResult 的項目。An IEnumerable<T> that contains elements of type TResult that are obtained by performing a grouped 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 GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>) 來執行兩個序列的群組聯結。The following code example demonstrates how to use GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>) to perform a grouped join on two sequences.

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

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

public static void GroupJoinEx1()
{
    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 where each element is an anonymous
    // type that contains a person's name and
    // a collection of names of the pets they own.
    var query =
        people.GroupJoin(pets,
                         person => person,
                         pet => pet.Owner,
                         (person, petCollection) =>
                             new
                             {
                                 OwnerName = person.Name,
                                 Pets = petCollection.Select(pet => pet.Name)
                             });

    foreach (var obj in query)
    {
        // Output the owner's name.
        Console.WriteLine("{0}:", obj.OwnerName);
        // Output each of the owner's pet's names.
        foreach (string pet in obj.Pets)
        {
            Console.WriteLine("  {0}", pet);
        }
    }
}

/*
 This code produces the following output:

 Hedlund, Magnus:
   Daisy
 Adams, Terry:
   Barley
   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 GroupJoinEx1()
    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 collection where each element is an anonymous type
    ' that contains a Person's name and a collection of names of 
    ' the pets that are owned by them.
    Dim query =
people.GroupJoin(pets,
           Function(person) person,
           Function(pet) pet.Owner,
           Function(person, petCollection) _
               New With {.OwnerName = person.Name,
                         .Pets = petCollection.Select(
                                            Function(pet) pet.Name)})

    Dim output As New System.Text.StringBuilder
    For Each obj In query
        ' Output the owner's name.
        output.AppendLine(obj.OwnerName & ":")
        ' Output each of the owner's pet's names.
        For Each pet As String In obj.Pets
            output.AppendLine("  " & pet)
        Next
    Next

    ' Display the output.
    Console.WriteLine(output.ToString)
End Sub

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

備註

這個方法是使用延後執行所執行。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不會執行,直到以 GetEnumerator foreach Visual c # 或 Visual Basic 中的方法來列舉物件為止 For EachThe 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.

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

GroupJoin 產生階層式結果,這表示的專案 outer 會與相符專案的集合配對 innerGroupJoin produces hierarchical results, which means that elements from outer are paired with collections of matching elements from inner. GroupJoin 可讓您根據的每個專案,以整個相符專案為基礎來建立結果 outerGroupJoin enables you to base your results on a whole set of matches for each element of outer.

注意

如果的指定專案中沒有相互關聯的專案 inner outer ,則該元素的相符序列將會是空的,但仍會出現在結果中。If there are no correlated elements in inner for a given element of outer, the sequence of matches for that element will be empty but will still appear in the results.

函式 resultSelector 只會針對每個專案呼叫一次, outer 並將所有 inner 符合該專案的元素集合 outerThe resultSelector function is called only one time for each outer element together with a collection of all the inner elements that match the outer element. 這不同于 Join 方法,其中的結果選取器函式會在包含一個專案的配對上叫用, outer 而另一個元素則叫用 innerThis differs from the Join method, in which the result selector function is invoked on pairs that contain one element from outer and one element from inner.

GroupJoin 保留的元素順序,以及的 outer 每個專案的順序 outer ,與相符元素的順序 innerGroupJoin preserves the order of the elements of outer, and for each element of outer, the order of the matching elements from inner.

GroupJoin 在傳統關係資料庫詞彙中沒有直接對等專案。GroupJoin has no direct equivalent in traditional relational database terms. 不過,這個方法會執行內部聯結和左方外部聯結的超集合。However, this method does implement a superset of inner joins and left outer joins. 這兩種作業都可以根據群組聯結來撰寫。Both of these operations can be written in terms of a grouped join. 請參閱 聯結作業See Join Operations.

在查詢運算式語法中, join … into (Visual c # ) 或 Group Join (Visual Basic) 子句會轉譯為的調用 GroupJoinIn query expression syntax, a join … into (Visual C#) or Group Join (Visual Basic) clause translates to an invocation of GroupJoin.

另請參閱

適用於

產品 Introduced