Enumerable.GroupJoin メソッド

キーが等しいかどうかに基づいて 2 つのシーケンスの要素を相互に関連付け、その結果をグループ化します。Correlates the elements of two sequences based on key equality and groups the results. 指定された IEqualityComparer<T> を使用してキーを比較します。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);

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)

型パラメーター

パラメーター

戻り値

例外

注釈

このメソッドは、遅延実行を使用して実装されます。This method is implemented by using deferred execution. イミディエイトの戻り値は、アクションを実行するために必要なすべての情報を格納するオブジェクトです。The immediate return value is an object that stores all the information that is required to perform the action. か、呼び出すことによって、オブジェクトが列挙されるまで、このメソッドによって表されるクエリは実行されません、GetEnumeratorメソッドを使用して直接またはforeachVisual C# またはFor EachVisual Basic で。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.

comparer が null場合は、既定の等値比較子である Defaultが使用され、キーのハッシュと比較に使用されます。If comparer is null, the default equality comparer, Default, is used to hash and compare keys.

GroupJoin では、階層の結果が生成されます。つまり、outer の要素は innerの一致する要素のコレクションとペアになります。GroupJoin produces hierarchical results, which means that elements from outer are paired with collections of matching elements from inner. GroupJoin を使用すると、outerの各要素について、一致した一連の結果に基づいて結果を生成できます。GroupJoin enables you to base your results on a whole set of matches for each element of outer.

resultSelector 関数は、outer の各要素に対して、outer 要素に一致するすべての inner 要素のコレクションと共に1回だけ呼び出されます。The 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. これは、outer からの1つの要素と innerの1つの要素を含むペアで結果セレクター関数が呼び出される Join メソッドとは異なります。This 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 は、outerの要素の順序を保持し、outerの各要素に対して innerからの一致する要素の順序を保持します。GroupJoin preserves the order of the elements of outer, and for each element of outer, the order of the matching elements from inner.

GroupJoin には、従来のリレーショナルデータベースの用語に直接相当するものはありません。GroupJoin has no direct equivalent in traditional relational database terms. ただし、このメソッドは内部結合と左外部結合のスーパーセットを実装します。However, this method does implement a superset of inner joins and left outer joins. これらの操作はどちらも、グループ化結合の観点から記述できます。Both of these operations can be written in terms of a grouped join. 「結合操作」を参照してください。See Join Operations.

こちらもご覧ください

• 結合操作の実行Performing Join Operations

キーが等しいかどうかに基づいて 2 つのシーケンスの要素を相互に関連付け、その結果をグループ化します。Correlates the elements of two sequences based on equality of keys and groups the results. キーの比較には既定の等値比較子が使用されます。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)

型パラメーター

パラメーター

戻り値

例外

例

次のコード例では、GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>,TResult>) を使用して、2つのシーケンスに対してグループ化結合を実行する方法を示します。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

注釈

このメソッドは、遅延実行を使用して実装されます。This method is implemented by using deferred execution. イミディエイトの戻り値は、アクションを実行するために必要なすべての情報を格納するオブジェクトです。The immediate return value is an object that stores all the information that is required to perform the action. か、呼び出すことによって、オブジェクトが列挙されるまで、このメソッドによって表されるクエリは実行されません、GetEnumeratorメソッドを使用して直接またはforeachVisual C# またはFor EachVisual Basic で。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.

既定の等値比較子である Defaultは、キーのハッシュおよび比較に使用されます。The default equality comparer, Default, is used to hash and compare keys.

GroupJoin では、階層の結果が生成されます。つまり、outer の要素は innerの一致する要素のコレクションとペアになります。GroupJoin produces hierarchical results, which means that elements from outer are paired with collections of matching elements from inner. GroupJoin を使用すると、outerの各要素について、一致した一連の結果に基づいて結果を生成できます。GroupJoin enables you to base your results on a whole set of matches for each element of outer.

resultSelector 関数は、outer の各要素に対して、outer 要素に一致するすべての inner 要素のコレクションと共に1回だけ呼び出されます。The 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. これは、Join メソッドとは異なります。結果セレクター関数は、outer からの1つの要素と innerの1つの要素を含むペアで呼び出されます。This 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 は、outerの要素の順序を保持し、outerの各要素に対して innerからの一致する要素の順序を保持します。GroupJoin preserves the order of the elements of outer, and for each element of outer, the order of the matching elements from inner.

GroupJoin には、従来のリレーショナルデータベースの用語に直接相当するものはありません。GroupJoin has no direct equivalent in traditional relational database terms. ただし、このメソッドは内部結合と左外部結合のスーパーセットを実装します。However, this method does implement a superset of inner joins and left outer joins. これらの操作はどちらも、グループ化結合の観点から記述できます。Both of these operations can be written in terms of a grouped join. 「結合操作」を参照してください。See Join Operations.

クエリ式の構文で、 join … into (Visual C#) またはGroup Joinの呼び出しに変換します (Visual Basic) 句GroupJoinします。In query expression syntax, a join … into (Visual C#) or Group Join (Visual Basic) clause translates to an invocation of GroupJoin.

こちらもご覧ください

• 結合操作Join Operations
• join 句 (C# リファレンス)join clause (C# Reference)
• Group Join 句 (Visual Basic)Group Join Clause (Visual Basic)