Enumerable.GroupBy Methode

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)

Typparameter

Parameter

Gibt zurück

IEnumerable<TResult>

Eine Auflistung von Elementen vom Typ TResult, wobei jedes Element eine Projektion über einer Gruppe und ihrem Schlüssel darstelltA collection of elements of type TResult where each element represents a projection over a group and its key.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie verwendet GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>) wird, um die projizierten Elemente einer Sequenz zu gruppieren und anschließend eine Sequenz von Ergebnissen vom Typ zu projizieren TResult .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.
    Console.WriteLine(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

Hinweise

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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);

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)

Typparameter

Parameter

Gibt zurück

IEnumerable<TResult>

Eine Auflistung von Elementen vom Typ TResult, wobei jedes Element eine Projektion über einer Gruppe und ihrem Schlüssel darstelltA collection of elements of type TResult where each element represents a projection over a group and its key.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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))

Typparameter

Parameter

Gibt zurück

IEnumerable<IGrouping<TKey,TElement>>

Ein IEnumerable<IGrouping<TKey, TElement>> in C# oder ein IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic, wobei jedes IGrouping<TKey,TElement>-Objekt eine Auflistung von Objekten des Typs TElement und einen Schlüssel enthältAn 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.

Ausnahmen

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie verwendet wird, GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) um die Elemente einer Sequenz zu gruppieren.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.
    Console.WriteLine(output.ToString)
End Sub

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

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Die Übersetzung des Abfrage Ausdrucks im folgenden Beispiel entspricht der Abfrage im obigen Beispiel.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

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .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.

Die- GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>) Methode gibt eine Auflistung von- IGrouping<TKey,TElement> Objekten zurück, eine für jeden eindeutigen Schlüssel, der gefunden wurde.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. Ein IGrouping<TKey,TElement> ist eine IEnumerable<T> , die auch über einen Schlüssel verfügt, der ihren Elementen zugeordnet ist.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Die IGrouping<TKey,TElement> Objekte werden in einer Reihenfolge zurückgegeben, die auf der Reihenfolge der Elemente in basiert source , die den ersten Schlüssel der einzelnen Schlüssel erzeugt haben IGrouping<TKey,TElement> .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>. Elemente in einer Gruppierung werden in der Reihenfolge ausgegeben, in der die Elemente, die Sie erstellt haben, in angezeigt werden source .Elements in a grouping are yielded in the order that the elements that produced them appear in source.

Der Standard Gleichheits Vergleich Default wird zum Vergleichen von Schlüsseln verwendet.The default equality comparer Default is used to compare keys.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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);

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))

Typparameter

Parameter

Gibt zurück

IEnumerable<IGrouping<TKey,TElement>>

Ein IEnumerable<IGrouping<TKey, TElement>> in C# oder ein IEnumerable(Of IGrouping(Of TKey, TElement)) in Visual Basic, wobei jedes IGrouping<TKey,TElement>-Objekt eine Auflistung von Objekten des Typs TElement und einen Schlüssel enthältAn 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.

Ausnahmen

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .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.

Die- GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>) Methode gibt eine Auflistung von- IGrouping<TKey,TElement> Objekten zurück, eine für jeden eindeutigen Schlüssel, der gefunden wurde.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. Ein IGrouping<TKey,TElement> ist eine IEnumerable<T> , die auch über einen Schlüssel verfügt, der ihren Elementen zugeordnet ist.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Die IGrouping<TKey,TElement> Objekte werden in einer Reihenfolge zurückgegeben, die auf der Reihenfolge der Elemente in basiert source , die den ersten Schlüssel der einzelnen Schlüssel erzeugt haben IGrouping<TKey,TElement> .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>. Elemente in einer Gruppierung werden in der Reihenfolge ausgegeben, in der die Elemente, die Sie erstellt haben, in angezeigt werden source .Elements in a grouping are yielded in the order that the elements that produced them appear in source.

Wenn comparer null den Wert hat, wird der Standard Gleichheits Vergleich Default verwendet, um Schlüssel zu vergleichen.If comparer is null, the default equality comparer Default is used to compare keys.

Wenn zwei Schlüssel gemäß als gleich betrachtet werden comparer , wird der erste Schlüssel als Schlüssel für diese Gruppierung ausgewählt.If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Weitere Informationen und Verwendungs Beispiele finden Sie unter Group-Klausel und Group By-Klausel.For more information and usage examples, see group clause and Group By Clause.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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)

Typparameter

Parameter

Gibt zurück

IEnumerable<TResult>

Eine Auflistung von Elementen vom Typ TResult, wobei jedes Element eine Projektion über einer Gruppe und ihrem Schlüssel darstelltA collection of elements of type TResult where each element represents a projection over a group and its key.

Beispiele

Im folgenden Codebeispiel wird veranschaulicht, wie verwendet wird, GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>) um die Elemente einer Sequenz zu gruppieren und eine Sequenz von Ergebnissen vom Typ zu projizieren TResult .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.
    Console.WriteLine(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

Hinweise

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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);

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)

Typparameter

Parameter

Gibt zurück

IEnumerable<TResult>

Eine Auflistung von Elementen vom Typ TResult, wobei jedes Element eine Projektion über einer Gruppe und ihrem Schlüssel darstelltA collection of elements of type TResult where each element represents a projection over a group and its key.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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))

Typparameter

Parameter

Gibt zurück

IEnumerable<IGrouping<TKey,TSource>>

Ein IEnumerable<IGrouping<TKey, TSource>> in C# oder ein IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic, wobei jedes IGrouping<TKey,TElement>-Objekt eine Sequenz von Objekten und einen Schlüssel enthältAn 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.

Ausnahmen

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .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.

Die- GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>) Methode gibt eine Auflistung von- IGrouping<TKey,TElement> Objekten zurück, eine für jeden eindeutigen Schlüssel, der gefunden wurde.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. Ein IGrouping<TKey,TElement> ist eine IEnumerable<T> , die auch über einen Schlüssel verfügt, der ihren Elementen zugeordnet ist.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Die IGrouping<TKey,TElement> Objekte werden in einer Reihenfolge zurückgegeben, die auf der Reihenfolge der Elemente in basiert source , die den ersten Schlüssel der einzelnen Schlüssel erzeugt haben IGrouping<TKey,TElement> .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>. Elemente in einer Gruppierung werden in der Reihenfolge zurückgegeben, in der Sie angezeigt werden source .Elements in a grouping are yielded in the order they appear in source.

Der Standard Gleichheits Vergleich Default wird zum Vergleichen von Schlüsseln verwendet.The default equality comparer Default is used to compare keys.

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Weitere Informationen und Verwendungs Beispiele finden Sie unter Group-Klausel und Group By-Klausel.For more information and usage examples, see group clause and Group By Clause.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)

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);

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))

Typparameter

Parameter

Gibt zurück

IEnumerable<IGrouping<TKey,TSource>>

Ein IEnumerable<IGrouping<TKey, TSource>> in C# oder ein IEnumerable(Of IGrouping(Of TKey, TSource)) in Visual Basic, wobei jedes IGrouping<TKey,TElement>-Objekt eine Auflistung von Objekten und einen Schlüssel enthältAn 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.

Ausnahmen

Hinweise

Diese Methode wird mithilfe von verzögerter Ausführung implementiert.This method is implemented by using deferred execution. Der unmittelbare Rückgabewert ist ein Objekt, das alle Informationen speichert, die zum Ausführen der Aktion erforderlich sind.The immediate return value is an object that stores all the information that is required to perform the action. Die durch diese Methode dargestellte Abfrage wird erst ausgeführt, wenn das Objekt durch Aufrufen der- GetEnumerator Methode direkt oder mithilfe von foreach in Visual c# oder in Visual Basic aufgezählt wird For Each .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.

Die- GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>) Methode gibt eine Auflistung von- IGrouping<TKey,TElement> Objekten zurück, eine für jeden eindeutigen Schlüssel, der gefunden wurde.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. Ein IGrouping<TKey,TElement> ist eine IEnumerable<T> , die auch über einen Schlüssel verfügt, der ihren Elementen zugeordnet ist.An IGrouping<TKey,TElement> is an IEnumerable<T> that also has a key associated with its elements.

Die IGrouping<TKey,TElement> Objekte werden in einer Reihenfolge zurückgegeben, die auf der Reihenfolge der Elemente in basiert source , die den ersten Schlüssel der einzelnen Schlüssel erzeugt haben IGrouping<TKey,TElement> .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>. Elemente in einer Gruppierung werden in der Reihenfolge zurückgegeben, in der Sie angezeigt werden source .Elements in a grouping are yielded in the order they appear in source.

Wenn comparer null den Wert hat, wird der Standard Gleichheits Vergleich Default verwendet, um Schlüssel zu vergleichen.If comparer is null, the default equality comparer Default is used to compare keys.

Wenn zwei Schlüssel gemäß als gleich betrachtet werden comparer , wird der erste Schlüssel als Schlüssel für diese Gruppierung ausgewählt.If two keys are considered equal according to comparer, the first key is chosen as the key for that grouping.

In der Abfrage Ausdruckssyntax wird eine group by (Visual c#)-oder Group By Into (Visual Basic)-Klausel in einen Aufruf von übersetzt GroupBy .In query expression syntax, a group by (Visual C#) or Group By Into (Visual Basic) clause translates to an invocation of GroupBy. Weitere Informationen und Verwendungs Beispiele finden Sie unter Group-Klausel und Group By-Klausel.For more information and usage examples, see group clause and Group By Clause.

Siehe auch

• group-Klausel (C#-Referenz)group clause (C# Reference)
• GROUP BY-Klausel (Visual Basic)Group By Clause (Visual Basic)