Enumerable.GroupBy メソッド

定義

シーケンスの要素をグループ化します。Groups the elements of a sequence.

オーバーロード

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 各グループの要素は、指定された関数を使用して射影されます。The elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. キー値の比較には、指定された比較子を使用し、各グループの要素の射影には、指定された関数を使用します。Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、指定された関数を使用して各グループの要素を射影します。Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

キー セレクター関数に従ってシーケンスの要素をグループ化します。Groups the elements of a sequence according to a key selector function. キーの比較には、比較子を使用し、各グループの要素の射影には、指定された関数を使用します。The keys are compared by using a comparer and each group's elements are projected by using a specified function.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. キーの比較には、指定された比較子を使用します。The keys are compared by using a specified comparer.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化します。Groups the elements of a sequence according to a specified key selector function.

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、指定された比較子を使用してキーを比較します。Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 各グループの要素は、指定された関数を使用して射影されます。The elements of each group are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult> resultSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * Func<'Key, seq<'Element>, 'Result> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), resultSelector As Func(Of TKey, IEnumerable(Of TElement), TResult)) As IEnumerable(Of TResult)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TElement

IGrouping<TKey,TElement> の要素の型。The type of the elements in each IGrouping<TKey,TElement>.

TResult

resultSelector によって返される結果値の型。The type of the result value returned by resultSelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

ソースの各要素を IGrouping<TKey,TElement> の要素に割り当てる関数。A function to map each source element to an element in an IGrouping<TKey,TElement>.

resultSelector
Func<TKey,IEnumerable<TElement>,TResult>

各グループから結果値を作成する関数。A function to create a result value from each group.

戻り値

IEnumerable<TResult>

TResult 型の要素のコレクション。各要素は、グループとそのキーの射影を表します。A collection of elements of type TResult where each element represents a projection over a group and its key.

次のコード例では GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) を使用してシーケンスの射影された要素をグループ化し、型 TResult の結果のシーケンスを射影する方法を示します。The following code example demonstrates how to use GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) to group the projected elements of a sequence and then project a sequence of results of type TResult.

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

public static void GroupByEx4()
{
    // Create a list of pets.
    List<Pet> petsList =
        new List<Pet>{ new Pet { Name="Barley", Age=8.3 },
                       new Pet { Name="Boots", Age=4.9 },
                       new Pet { Name="Whiskers", Age=1.5 },
                       new Pet { Name="Daisy", Age=4.3 } };

    // Group Pet.Age values by the Math.Floor of the age.
    // Then project an anonymous type from each group
    // that consists of the key, the count of the group's
    // elements, and the minimum and maximum age in the group.
    var query = petsList.GroupBy(
        pet => Math.Floor(pet.Age),
        pet => pet.Age,
        (baseAge, ages) => new
        {
            Key = baseAge,
            Count = ages.Count(),
            Min = ages.Min(),
            Max = ages.Max()
        });

    // Iterate over each anonymous type.
    foreach (var result in query)
    {
        Console.WriteLine("\nAge group: " + result.Key);
        Console.WriteLine("Number of pets in this age group: " + result.Count);
        Console.WriteLine("Minimum age: " + result.Min);
        Console.WriteLine("Maximum age: " + result.Max);
    }

    /*  This code produces the following output:
     
        Age group: 8
        Number of pets in this age group: 1
        Minimum age: 8.3
        Maximum age: 8.3
     
        Age group: 4
        Number of pets in this age group: 2
        Minimum age: 4.3
        Maximum age: 4.9
     
        Age group: 1
        Number of pets in this age group: 1
        Minimum age: 1.5
        Maximum age: 1.5
    */
}
Structure Pet
    Public Name As String
    Public Age As Double
End Structure

Public Sub GroupByEx4()
    ' Create a list of pets.
    Dim petsList As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8.3},
                          New Pet With {.Name = "Boots", .Age = 4.9},
                          New Pet With {.Name = "Whiskers", .Age = 1.5},
                          New Pet With {.Name = "Daisy", .Age = 4.3}})

    ' Group Pet.Age values by the Math.Floor of the age.
    ' Then project an anonymous type from each group
    ' that consists of the key, the count of the group's
    ' elements, and the minimum and maximum age in the group.
    Dim query = petsList.GroupBy(
Function(pet) Math.Floor(pet.Age),
Function(pet) pet.Age,
Function(baseAge, ages) New With
    {.Key = baseAge,
    .Count = ages.Count(),
    .Min = ages.Min(),
    .Max = ages.Max()}
)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each anonymous type.
    For Each result In query
        output.AppendLine(vbCrLf & "Age group: " & result.Key)
        output.AppendLine("Number of pets in this age group: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

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

' This code produces the following output:

' Age group: 8
' Number of pets in this age group: 1
' Minimum age: 8.3
' Maximum age: 8.3
'
' Age group: 4
' Number of pets in this age group: 2
' Minimum age: 4.3
' Maximum age: 4.9
'
' Age group: 1
' Number of pets in this age group: 1
' Minimum age: 1.5
' Maximum age: 1.5

注釈

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

こちらもご覧ください

GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. キー値の比較には、指定された比較子を使用し、各グループの要素の射影には、指定された関数を使用します。Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * Func<'Key, seq<'Element>, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), resultSelector As Func(Of TKey, IEnumerable(Of TElement), TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TElement

IGrouping<TKey,TElement> の要素の型。The type of the elements in each IGrouping<TKey,TElement>.

TResult

resultSelector によって返される結果値の型。The type of the result value returned by resultSelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

ソースの各要素を IGrouping<TKey,TElement> の要素に割り当てる関数。A function to map each source element to an element in an IGrouping<TKey,TElement>.

resultSelector
Func<TKey,IEnumerable<TElement>,TResult>

各グループから結果値を作成する関数。A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

キーの比較対象となる IEqualityComparer<T>An IEqualityComparer<T> to compare keys with.

戻り値

IEnumerable<TResult>

TResult 型の要素のコレクション。各要素は、グループとそのキーの射影を表します。A collection of elements of type TResult where each element represents a projection over a group and its key.

こちらもご覧ください

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、指定された関数を使用して各グループの要素を射影します。Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TElement> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> -> seq<System.Linq.IGrouping<'Key, 'Element>>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement)) As IEnumerable(Of IGrouping(Of TKey, TElement))

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TElement

IGrouping<TKey,TElement> 内の要素の型。The type of the elements in the IGrouping<TKey,TElement>.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

ソースの各要素を IGrouping<TKey,TElement> の要素に割り当てる関数。A function to map each source element to an element in the IGrouping<TKey,TElement>.

戻り値

IEnumerable<IGrouping<TKey,TElement>>

C# では IEnumerable<IGrouping<TKey, TElement>>、Visual Basic では IEnumerable(Of IGrouping(Of TKey, TElement))。各 IGrouping<TKey,TElement> オブジェクトには、TElement 型のオブジェクトのコレクションとキーが含まれます。An IEnumerable<IGrouping<TKey, TElement>> in C# or IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects of type TElement and a key.

例外

sourcekeySelector、または elementSelector は、null です。source or keySelector or elementSelector is null.

次のコード例は、GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) を使用してシーケンスの要素をグループ化する方法を示しています。The following code example demonstrates how to use GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) to group the elements of a sequence.

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

// Uses method-based query syntax.
public static void GroupByEx1()
{
    // Create a list of pets.
    List<Pet> pets =
        new List<Pet>{ new Pet { Name="Barley", Age=8 },
                       new Pet { Name="Boots", Age=4 },
                       new Pet { Name="Whiskers", Age=1 },
                       new Pet { Name="Daisy", Age=4 } };

    // Group the pets using Age as the key value 
    // and selecting only the pet's Name for each value.
    IEnumerable<IGrouping<int, string>> query =
        pets.GroupBy(pet => pet.Age, pet => pet.Name);

    // Iterate over each IGrouping in the collection.
    foreach (IGrouping<int, string> petGroup in query)
    {
        // Print the key value of the IGrouping.
        Console.WriteLine(petGroup.Key);
        // Iterate over each value in the 
        // IGrouping and print the value.
        foreach (string name in petGroup)
            Console.WriteLine("  {0}", name);
    }
}

/*
 This code produces the following output:

 8
   Barley
 4
   Boots
   Daisy
 1
   Whiskers
*/
Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Sub GroupByEx1()
    'Create a list of Pet objects.
    Dim pets As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8},
                          New Pet With {.Name = "Boots", .Age = 4},
                          New Pet With {.Name = "Whiskers", .Age = 1},
                          New Pet With {.Name = "Daisy", .Age = 4}})

    ' Group the pets using Age as the key 
    ' and selecting only the pet's Name for each value.
    Dim query As IEnumerable(Of IGrouping(Of Integer, String)) =
pets.GroupBy(Function(pet) pet.Age,
             Function(pet) pet.Name)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each IGrouping in the collection.
    For Each petGroup As IGrouping(Of Integer, String) In query
        ' Print the key value of the IGrouping.
        output.AppendLine(petGroup.Key)
        ' Iterate over each value in the IGrouping and print the value.
        For Each name As String In petGroup
            output.AppendLine("  " & name)
        Next
    Next

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

' This code produces the following output:
'
' 8
'   Barley
' 4
'   Boots
'   Daisy
' 1
'   Whiskers

クエリ式の構文で、 group by (Visual C#) またはGroup By Intoの呼び出しに変換します (Visual Basic) 句GroupByします。In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. 次の例のクエリ式の変換は、上記の例のクエリに相当します。The translation of the query expression in the following example is equivalent to the query in the example above.

IEnumerable<IGrouping<int, string>> query =
    from pet in pets
    group pet.Name by pet.Age;
    Dim query =
From pet In pets
Group pet.Name By Age = pet.Age Into ageGroup = Group

注意

Visual C# または Visual Basic のクエリ式で、要素とキーの選択式は、逆の順序でへの呼び出しの引数の位置から、GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)メソッド。In a Visual C# or Visual Basic query expression, the element and key selection expressions occur in the reverse order from their argument positions in a call to the GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method.

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.

@No__t-0 メソッドは、検出された個別のキーごとに1つずつ、@no__t オブジェクトのコレクションを返します。The GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. @No__t-0 は、要素に関連付けられたキーも持つ IEnumerable<T> です。An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

@No__t 0 のオブジェクトは、各 IGrouping<TKey,TElement> の最初のキーを生成した source の要素の順序に基づいて並べ替えられます。The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. グループ内の要素は、それを生成した要素が @no__t 0 に出現する順序で表示されます。Elements in a grouping are yielded in the order that the elements that produced them appear in source.

既定の等値比較子 Default を使用してキーを比較します。The default equality comparer Default is used to compare keys.

こちらもご覧ください

GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)

キー セレクター関数に従ってシーケンスの要素をグループ化します。Groups the elements of a sequence according to a key selector function. キーの比較には、比較子を使用し、各グループの要素の射影には、指定された関数を使用します。The keys are compared by using a comparer and each group's elements are projected by using a specified function.

public:
generic <typename TSource, typename TKey, typename TElement>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TElement> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TSource, TElement> ^ elementSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Source, 'Element> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<System.Linq.IGrouping<'Key, 'Element>>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), elementSelector As Func(Of TSource, TElement), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of IGrouping(Of TKey, TElement))

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TElement

IGrouping<TKey,TElement> 内の要素の型。The type of the elements in the IGrouping<TKey,TElement>.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

elementSelector
Func<TSource,TElement>

ソースの各要素を IGrouping<TKey,TElement> の要素に割り当てる関数。A function to map each source element to an element in an IGrouping<TKey,TElement>.

comparer
IEqualityComparer<TKey>

キーを比較する IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

戻り値

IEnumerable<IGrouping<TKey,TElement>>

C# では IEnumerable<IGrouping<TKey, TElement>>、Visual Basic では IEnumerable(Of IGrouping(Of TKey, TElement))。各 IGrouping<TKey,TElement> オブジェクトには、TElement 型のオブジェクトのコレクションとキーが含まれます。An IEnumerable<IGrouping<TKey, TElement>> in C# or IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects of type TElement and a key.

例外

sourcekeySelector、または elementSelector は、null です。source or keySelector or elementSelector is null.

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.

@No__t-0 メソッドは、検出された個別のキーごとに1つずつ、@no__t オブジェクトのコレクションを返します。The GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. @No__t-0 は、要素に関連付けられたキーも持つ IEnumerable<T> です。An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

@No__t 0 のオブジェクトは、各 IGrouping<TKey,TElement> の最初のキーを生成した source の要素の順序に基づいて並べ替えられます。The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. グループ内の要素は、それを生成した要素が @no__t 0 に出現する順序で表示されます。Elements in a grouping are yielded in the order that the elements that produced them appear in source.

@No__t-0 が null の場合、キーの比較には既定の等値比較子 Default が使用されます。If comparer is null, the default equality comparer Default is used to compare keys.

@No__t-0 に従って2つのキーが等しいと見なされた場合、そのグループのキーとして最初のキーが選択されます。If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

クエリ式の構文で、 group by (Visual C#) またはGroup By Intoの呼び出しに変換します (Visual Basic) 句GroupByします。In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. 詳細と使用例については、「 group 句group by 句」を参照してください。For more information and usage examples, see group clause and Group By Clause.

こちらもご覧ください

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.

public:
generic <typename TSource, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TKey, System::Collections::Generic::IEnumerable<TSource> ^, TResult> ^ resultSelector);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TKey,System.Collections.Generic.IEnumerable<TSource>,TResult> resultSelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Key, seq<'Source>, 'Result> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), resultSelector As Func(Of TKey, IEnumerable(Of TSource), TResult)) As IEnumerable(Of TResult)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TResult

resultSelector によって返される結果値の型。The type of the result value returned by resultSelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

resultSelector
Func<TKey,IEnumerable<TSource>,TResult>

各グループから結果値を作成する関数。A function to create a result value from each group.

戻り値

IEnumerable<TResult>

TResult 型の要素のコレクション。各要素は、グループとそのキーの射影を表します。A collection of elements of type TResult where each element represents a projection over a group and its key.

次のコード例では、GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) を使用してシーケンスの要素をグループ化し、プロジェクトの種類 TResult の一連の結果を射影する方法を示します。The following code example demonstrates how to use GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) to group the elements of a sequence and project a sequence of results of type TResult.

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

public static void GroupByEx3()
{
    // Create a list of pets.
    List<Pet> petsList =
        new List<Pet>{ new Pet { Name="Barley", Age=8.3 },
                       new Pet { Name="Boots", Age=4.9 },
                       new Pet { Name="Whiskers", Age=1.5 },
                       new Pet { Name="Daisy", Age=4.3 } };

    // Group Pet objects by the Math.Floor of their age.
    // Then project an anonymous type from each group
    // that consists of the key, the count of the group's
    // elements, and the minimum and maximum age in the group.
    var query = petsList.GroupBy(
        pet => Math.Floor(pet.Age),
        (age, pets) => new
        {
            Key = age,
            Count = pets.Count(),
            Min = pets.Min(pet => pet.Age),
            Max = pets.Max(pet => pet.Age)
        });

    // Iterate over each anonymous type.
    foreach (var result in query)
    {
        Console.WriteLine("\nAge group: " + result.Key);
        Console.WriteLine("Number of pets in this age group: " + result.Count);
        Console.WriteLine("Minimum age: " + result.Min);
        Console.WriteLine("Maximum age: " + result.Max);
    }

    /*  This code produces the following output:
     
        Age group: 8
        Number of pets in this age group: 1
        Minimum age: 8.3
        Maximum age: 8.3
     
        Age group: 4
        Number of pets in this age group: 2
        Minimum age: 4.3
        Maximum age: 4.9
     
        Age group: 1
        Number of pets in this age group: 1
        Minimum age: 1.5
        Maximum age: 1.5
    */
}
Structure Pet
    Public Name As String
    Public Age As Double
End Structure

Public Sub GroupByEx3()
    ' Create a list of pets.
    Dim petsList As New List(Of Pet)(New Pet() _
                         {New Pet With {.Name = "Barley", .Age = 8.3},
                          New Pet With {.Name = "Boots", .Age = 4.9},
                          New Pet With {.Name = "Whiskers", .Age = 1.5},
                          New Pet With {.Name = "Daisy", .Age = 4.3}})

    ' Group Pet objects by the Math.Floor of their age.
    ' Then project an anonymous type from each group
    ' that consists of the key, the count of the group's
    ' elements, and the minimum and maximum age in the group.
    Dim query = petsList.GroupBy(
Function(pet) Math.Floor(pet.Age),
Function(age, pets) New With
    {.Key = age,
    .Count = pets.Count(),
    .Min = pets.Min(Function(pet) pet.Age),
    .Max = pets.Max(Function(Pet) Pet.Age)}
)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each anonymous type.
    For Each result In query
        output.AppendLine(vbCrLf & "Age group: " & result.Key)
        output.AppendLine("Number of pets in this age group: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

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

' This code produces the following output:

' Age group: 8
' Number of pets in this age group: 1
' Minimum age: 8.3
' Maximum age: 8.3
'
' Age group: 4
' Number of pets in this age group: 2
' Minimum age: 4.3
' Maximum age: 4.9
'
' Age group: 1
' Number of pets in this age group: 1
' Minimum age: 1.5
' Maximum age: 1.5

注釈

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

こちらもご覧ください

GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、各グループとそのキーから結果値を作成します。Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. キーの比較には、指定された比較子を使用します。The keys are compared by using a specified comparer.

public:
generic <typename TSource, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<TResult> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, Func<TKey, System::Collections::Generic::IEnumerable<TSource> ^, TResult> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<TResult> GroupBy<TSource,TKey,TResult> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TKey,System.Collections.Generic.IEnumerable<TSource>,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * Func<'Key, seq<'Source>, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TResult) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), resultSelector As Func(Of TKey, IEnumerable(Of TSource), TResult), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of TResult)

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

TResult

resultSelector によって返される結果値の型。The type of the result value returned by resultSelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

resultSelector
Func<TKey,IEnumerable<TSource>,TResult>

各グループから結果値を作成する関数。A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

キーの比較対象となる IEqualityComparer<T>An IEqualityComparer<T> to compare keys with.

戻り値

IEnumerable<TResult>

TResult 型の要素のコレクション。各要素は、グループとそのキーの射影を表します。A collection of elements of type TResult where each element represents a projection over a group and its key.

こちらもご覧ください

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化します。Groups the elements of a sequence according to a specified key selector function.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> -> seq<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey)) As IEnumerable(Of IGrouping(Of TKey, TSource))

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

戻り値

IEnumerable<IGrouping<TKey,TSource>>

C# では IEnumerable<IGrouping<TKey, TSource>>、Visual Basic では IEnumerable(Of IGrouping(Of TKey, TSource))。各 IGrouping<TKey,TElement> オブジェクトには、オブジェクトのシーケンスとキーが含まれます。An IEnumerable<IGrouping<TKey, TSource>> in C# or IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> object contains a sequence of objects and a key.

例外

source または keySelectornull です。source or keySelector is null.

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.

@No__t-0 メソッドは、検出された個別のキーごとに1つずつ、@no__t オブジェクトのコレクションを返します。The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. @No__t-0 は、要素に関連付けられたキーも持つ IEnumerable<T> です。An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

@No__t 0 のオブジェクトは、各 IGrouping<TKey,TElement> の最初のキーを生成した source の要素の順序に基づいて並べ替えられます。The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. グループ内の要素は、source に出現する順序で生成されます。Elements in a grouping are yielded in the order they appear in source.

既定の等値比較子 Default を使用してキーを比較します。The default equality comparer Default is used to compare keys.

クエリ式の構文で、 group by (Visual C#) またはGroup By Intoの呼び出しに変換します (Visual Basic) 句GroupByします。In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. 詳細と使用例については、「 group 句group by 句」を参照してください。For more information and usage examples, see group clause and Group By Clause.

こちらもご覧ください

GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)

指定されたキー セレクター関数に従ってシーケンスの要素をグループ化し、指定された比較子を使用してキーを比較します。Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.

public:
generic <typename TSource, typename TKey>
[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Collections::Generic::IEnumerable<TSource> ^ source, Func<TSource, TKey> ^ keySelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
static member GroupBy : seq<'Source> * Func<'Source, 'Key> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IEnumerable(Of TSource), keySelector As Func(Of TSource, TKey), comparer As IEqualityComparer(Of TKey)) As IEnumerable(Of IGrouping(Of TKey, TSource))

型パラメーター

TSource

source の要素の型。The type of the elements of source.

TKey

keySelector によって返されるキーの型。The type of the key returned by keySelector.

パラメーター

source
IEnumerable<TSource>

グループ化する要素を含む IEnumerable<T>An IEnumerable<T> whose elements to group.

keySelector
Func<TSource,TKey>

各要素のキーを抽出する関数。A function to extract the key for each element.

comparer
IEqualityComparer<TKey>

キーを比較する IEqualityComparer<T>An IEqualityComparer<T> to compare keys.

戻り値

IEnumerable<IGrouping<TKey,TSource>>

C# では IEnumerable<IGrouping<TKey, TSource>>、Visual Basic では IEnumerable(Of IGrouping(Of TKey, TSource))。各 IGrouping<TKey,TElement> オブジェクトには、オブジェクトのコレクションとキーが含まれます。An IEnumerable<IGrouping<TKey, TSource>> in C# or IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> object contains a collection of objects and a key.

例外

source または keySelectornull です。source or keySelector is null.

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.

@No__t-0 メソッドは、検出された個別のキーごとに1つずつ、@no__t オブジェクトのコレクションを返します。The GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) method returns a collection of IGrouping<TKey,TElement> objects, one for each distinct key that was encountered. @No__t-0 は、要素に関連付けられたキーも持つ IEnumerable<T> です。An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

@No__t 0 のオブジェクトは、各 IGrouping<TKey,TElement> の最初のキーを生成した source の要素の順序に基づいて並べ替えられます。The IGrouping<TKey,TElement> objects are yielded in an order based on the order of the elements in source that produced the first key of each IGrouping<TKey,TElement>. グループ内の要素は、source に出現する順序で生成されます。Elements in a grouping are yielded in the order they appear in source.

@No__t-0 が null の場合、キーの比較には既定の等値比較子 Default が使用されます。If comparer is null, the default equality comparer Default is used to compare keys.

@No__t-0 に従って2つのキーが等しいと見なされた場合、そのグループのキーとして最初のキーが選択されます。If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

クエリ式の構文で、 group by (Visual C#) またはGroup By Intoの呼び出しに変換します (Visual Basic) 句GroupByします。In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. 詳細と使用例については、「 group 句group by 句」を参照してください。For more information and usage examples, see group clause and Group By Clause.

こちらもご覧ください

適用対象