Queryable.GroupBy 메서드

정의

시퀀스의 요소를 그룹화합니다.Groups the elements of a sequence.

오버로드

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 키는 지정된 비교자를 통해 비교되고 각 그룹의 요소는 지정된 함수를 통해 투영됩니다.Keys are compared by using a specified comparer and the elements of each group are projected by using a specified function.

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 각 그룹의 요소는 지정된 함수를 통해 투영됩니다.The elements of each group are projected by using a specified function.

GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>)

지정된 키 선택기 함수에 따라 시퀀스의 요소를 그룹화하고 지정된 함수를 사용하여 각 그룹의 요소를 투영합니다.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>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>)

시퀀스의 요소를 그룹화하고 지정된 함수를 사용하여 각 그룹의 요소를 투영합니다.Groups the elements of a sequence and projects the elements for each group by using a specified function. 키 값은 지정된 비교자를 통해 비교됩니다.Key values are compared by using a specified comparer.

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.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>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>)

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 키는 지정된 비교자를 통해 비교됩니다.Keys are compared by using a specified comparer.

GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>)

지정된 키 선택기 함수에 따라 지정된 비교자로 키를 비교하여 시퀀스의 요소를 그룹화합니다.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>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)

지정된 키 선택기 함수에 따라 시퀀스의 요소를 그룹화합니다.Groups the elements of a sequence according to a specified key selector function.

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 키는 지정된 비교자를 통해 비교되고 각 그룹의 요소는 지정된 함수를 통해 투영됩니다.Keys 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::Linq::IQueryable<TResult> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Linq::Expressions::Expression<Func<TSource, TElement> ^> ^ elementSelector, System::Linq::Expressions::Expression<Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Linq.IQueryable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Linq.Expressions.Expression<Func<TSource,TElement>> elementSelector, System.Linq.Expressions.Expression<Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
public static System.Linq.IQueryable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Linq.Expressions.Expression<Func<TSource,TElement>> elementSelector, System.Linq.Expressions.Expression<Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Linq.Expressions.Expression<Func<'Source, 'Element>> * System.Linq.Expressions.Expression<Func<'Key, seq<'Element>, 'Result>> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.IQueryable<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), elementSelector As Expression(Of Func(Of TSource, TElement)), resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TElement), TResult)), comparer As IEqualityComparer(Of TKey)) As IQueryable(Of TResult)

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TElement

IGrouping<TKey,TElement>에 있는 요소의 형식입니다.The type of the elements in each IGrouping<TKey,TElement>.

TResult

resultSelector에서 반환하는 결과 값의 형식입니다.The type of the result value returned by resultSelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

elementSelector
Expression<Func<TSource,TElement>>

각 소스 요소를 IGrouping<TKey,TElement>의 요소에 매핑하는 함수입니다.A function to map each source element to an element in an IGrouping<TKey,TElement>.

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

각 그룹의 결과 값을 만드는 함수입니다.A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

키를 비교할 IEqualityComparer<T>입니다.An IEqualityComparer<T> to compare keys.

반환

IQueryable<TResult>

형식 인수가 TResult이고 각 요소가 그룹 및 해당 키에 대한 프로젝션을 나타내는 T:System.Linq.IQueryable`1입니다.An T:System.Linq.IQueryable`1 that has a type argument of TResult and where each element represents a projection over a group and its key.

예외

source, keySelector, elementSelector, resultSelector 또는 comparernull인 경우source or keySelector or elementSelector or resultSelector or comparer is null.

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) .The GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source keySelector 각 요소에 대해를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다.The expected behavior is that it groups the elements of source by key values that are obtained by invoking keySelector on each element. comparer매개 변수는 키 값을 비교 하는 데 사용 됩니다.The comparer parameter is used to compare key values. elementSelector매개 변수는 각 그룹의 요소를 프로젝션 하는 데 사용 되 고, resultSelector 매개 변수는 각 그룹의 결과 값과 해당 키를 가져오는 데 사용 됩니다.The elementSelector parameter is used to project the elements of each group, and the resultSelector parameter is used to obtain a result value from each group and its key.

적용 대상

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 각 그룹의 요소는 지정된 함수를 통해 투영됩니다.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::Linq::IQueryable<TResult> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Linq::Expressions::Expression<Func<TSource, TElement> ^> ^ elementSelector, System::Linq::Expressions::Expression<Func<TKey, System::Collections::Generic::IEnumerable<TElement> ^, TResult> ^> ^ resultSelector);
public static System.Linq.IQueryable<TResult> GroupBy<TSource,TKey,TElement,TResult> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Linq.Expressions.Expression<Func<TSource,TElement>> elementSelector, System.Linq.Expressions.Expression<Func<TKey,System.Collections.Generic.IEnumerable<TElement>,TResult>> resultSelector);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Linq.Expressions.Expression<Func<'Source, 'Element>> * System.Linq.Expressions.Expression<Func<'Key, seq<'Element>, 'Result>> -> System.Linq.IQueryable<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement, TResult) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), elementSelector As Expression(Of Func(Of TSource, TElement)), resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TElement), TResult))) As IQueryable(Of TResult)

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TElement

IGrouping<TKey,TElement>에 있는 요소의 형식입니다.The type of the elements in each IGrouping<TKey,TElement>.

TResult

resultSelector에서 반환하는 결과 값의 형식입니다.The type of the result value returned by resultSelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

elementSelector
Expression<Func<TSource,TElement>>

각 소스 요소를 IGrouping<TKey,TElement>의 요소에 매핑하는 함수입니다.A function to map each source element to an element in an IGrouping<TKey,TElement>.

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

각 그룹의 결과 값을 만드는 함수입니다.A function to create a result value from each group.

반환

IQueryable<TResult>

형식 인수가 TResult이고 각 요소가 그룹 및 해당 키에 대한 프로젝션을 나타내는 T:System.Linq.IQueryable`1입니다.An T:System.Linq.IQueryable`1 that has a type argument of TResult and where each element represents a projection over a group and its key.

예외

source, keySelector, elementSelector 또는 resultSelectornull인 경우source or keySelector or elementSelector or resultSelector is null.

예제

다음 코드 예제에서는를 사용 하 여 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) 시퀀스의 요소를 그룹화 하 고 형식의 결과 시퀀스를 프로젝션 하는 방법을 보여 줍니다 TResult .The following code example demonstrates how to use GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,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 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.AsQueryable().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

Shared 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 valuesby 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.AsQueryable().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 with this age: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

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

    ' This code produces the following output:

    '  Age group: 8
    '  Number of pets with this age: 1
    '  Minimum age: 8.3
    '  Maximum age: 8.3

    '  Age group: 4
    '  Number of pets with this age: 2
    '  Minimum age: 4.3
    '  Maximum age: 4.9

    '  Age group: 1
    '  Number of pets with this age: 1
    '  Minimum age: 1.5
    '  Maximum age: 1.5
End Sub

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) .The GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey,IEnumerable<TElement>,TResult>>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source keySelector 각 요소에 대해를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다.The expected behavior is that it groups the elements of source by key values that are obtained by invoking keySelector on each element. elementSelector매개 변수는 각 그룹의 요소를 프로젝션 하는 데 사용 되 고, resultSelector 매개 변수는 각 그룹의 결과 값과 해당 키를 가져오는 데 사용 됩니다.The elementSelector parameter is used to project the elements of each group, and the resultSelector parameter is used to obtain a result value from each group and its key.

적용 대상

GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>)

지정된 키 선택기 함수에 따라 시퀀스의 요소를 그룹화하고 지정된 함수를 사용하여 각 그룹의 요소를 투영합니다.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::Linq::IQueryable<System::Linq::IGrouping<TKey, TElement> ^> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Linq::Expressions::Expression<Func<TSource, TElement> ^> ^ elementSelector);
public static System.Linq.IQueryable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Linq.Expressions.Expression<Func<TSource,TElement>> elementSelector);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Linq.Expressions.Expression<Func<'Source, 'Element>> -> System.Linq.IQueryable<System.Linq.IGrouping<'Key, 'Element>>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TElement) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), elementSelector As Expression(Of Func(Of TSource, TElement))) As IQueryable(Of IGrouping(Of TKey, TElement))

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TElement

IGrouping<TKey,TElement>에 있는 요소의 형식입니다.The type of the elements in each IGrouping<TKey,TElement>.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

elementSelector
Expression<Func<TSource,TElement>>

각 소스 요소를 IGrouping<TKey,TElement>의 요소에 매핑하는 함수입니다.A function to map each source element to an element in an IGrouping<TKey,TElement>.

반환

IQueryable<IGrouping<TKey,TElement>>

IGrouping<TKey,TElement>TElement 형식 개체 및 키의 시퀀스가 들어 있는 IQueryable<IGrouping<TKey, TElement>>(C#의 경우) 또는 IQueryable(Of IGrouping(Of TKey, TElement))(Visual Basic의 경우)입니다.An IQueryable<IGrouping<TKey, TElement>> in C# or IQueryable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> contains a sequence of objects of type TElement and a key.

예외

source, keySelector 또는 elementSelectornull인 경우source or keySelector or elementSelector is null.

예제

다음 코드 예제에서는를 사용 하 여 시퀀스의 요소를 그룹화 하는 방법을 보여 줍니다 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) .The following code example demonstrates how to use GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) to group the elements of a sequence.

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

public static void GroupByEx2()
{
    // Create a list of Pet objects.
    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 Pet.Age as the key.
    // Use Pet.Name as the value for each entry.
    IEnumerable<IGrouping<int, string>> query =
        pets.AsQueryable().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

Shared Sub GroupByEx2()
    ' 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 Pet.Age as the key.
    ' Use Pet.Name as the value for each entry.
    Dim query As IEnumerable(Of IGrouping(Of Integer, String)) = _
        pets.AsQueryable().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(String.Format("  {0}", name))
        Next
    Next

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

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

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) .The GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source 각 요소에서를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다 keySelector .The expected behavior is that it groups the elements of source by a key value that is obtained by invoking keySelector on each element. elementSelector각 요소에 대해를 호출 하 여 결과 요소를 가져옵니다.It invokes elementSelector on each element to obtain a result element.

적용 대상

GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>)

시퀀스의 요소를 그룹화하고 지정된 함수를 사용하여 각 그룹의 요소를 투영합니다.Groups the elements of a sequence and projects the elements for each group by using a specified function. 키 값은 지정된 비교자를 통해 비교됩니다.Key values are compared by using a specified comparer.

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

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TElement

IGrouping<TKey,TElement>에 있는 요소의 형식입니다.The type of the elements in each IGrouping<TKey,TElement>.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

elementSelector
Expression<Func<TSource,TElement>>

각 소스 요소를 IGrouping<TKey,TElement>의 요소에 매핑하는 함수입니다.A function to map each source element to an element in an IGrouping<TKey,TElement>.

comparer
IEqualityComparer<TKey>

키를 비교할 IEqualityComparer<T>입니다.An IEqualityComparer<T> to compare keys.

반환

IQueryable<IGrouping<TKey,TElement>>

IGrouping<TKey,TElement>TElement 형식 개체 및 키의 시퀀스가 들어 있는 IQueryable<IGrouping<TKey, TElement>>(C#의 경우) 또는 IQueryable(Of IGrouping(Of TKey, TElement))(Visual Basic의 경우)입니다.An IQueryable<IGrouping<TKey, TElement>> in C# or IQueryable(Of IGrouping(Of TKey, TElement)) in Visual Basic where each IGrouping<TKey,TElement> contains a sequence of objects of type TElement and a key.

예외

source, keySelector, elementSelector 또는 comparernull인 경우source or keySelector or elementSelector or comparer is null.

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) .The GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source 각 요소에서를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다 keySelector .The expected behavior is that it groups the elements of source by a key value that is obtained by invoking keySelector on each element. 키 값은를 사용 하 여 비교 됩니다 comparer .Key values are compared by using comparer. elementSelector각 요소에 대해 매개 변수를 호출 하 여 결과 요소를 가져옵니다.The elementSelector parameter is invoked on each element to obtain a result element.

적용 대상

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.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::Linq::IQueryable<TResult> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Linq::Expressions::Expression<Func<TKey, System::Collections::Generic::IEnumerable<TSource> ^, TResult> ^> ^ resultSelector);
public static System.Linq.IQueryable<TResult> GroupBy<TSource,TKey,TResult> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Linq.Expressions.Expression<Func<TKey,System.Collections.Generic.IEnumerable<TSource>,TResult>> resultSelector);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Linq.Expressions.Expression<Func<'Key, seq<'Source>, 'Result>> -> System.Linq.IQueryable<'Result>
<Extension()>
Public Function GroupBy(Of TSource, TKey, TResult) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TSource), TResult))) As IQueryable(Of TResult)

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TResult

resultSelector에서 반환하는 결과 값의 형식입니다.The type of the result value returned by resultSelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

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

각 그룹의 결과 값을 만드는 함수입니다.A function to create a result value from each group.

반환

IQueryable<TResult>

형식 인수가 TResult이고 각 요소가 그룹 및 해당 키에 대한 프로젝션을 나타내는 T:System.Linq.IQueryable`1입니다.An T:System.Linq.IQueryable`1 that has a type argument of TResult and where each element represents a projection over a group and its key.

예외

source, keySelector 또는 resultSelectornull인 경우source or keySelector or resultSelector is null.

예제

다음 코드 예제에서는를 사용 하 여 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 시퀀스의 요소를 그룹화 하 고 형식의 결과 시퀀스를 프로젝션 하는 방법을 보여 줍니다 TResult .The following code example demonstrates how to use GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<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.AsQueryable().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

Shared 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.AsQueryable().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 with this age: " & result.Count)
        output.AppendLine("Minimum age: " & result.Min)
        output.AppendLine("Maximum age: " & result.Max)
    Next

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

    ' This code produces the following output:

    '  Age group: 8
    '  Number of pets with this age: 1
    '  Minimum age: 8.3
    '  Maximum age: 8.3

    '  Age group: 4
    '  Number of pets with this age: 2
    '  Minimum age: 4.3
    '  Maximum age: 4.9

    '  Age group: 1
    '  Number of pets with this age: 1
    '  Minimum age: 1.5
    '  Maximum age: 1.5
End Sub

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) .The GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source 각 요소에서를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다 keySelector .The expected behavior is that it groups the elements of source by a key value that is obtained by invoking keySelector on each element. resultSelector매개 변수는 각 그룹의 결과 값과 해당 키를 가져오는 데 사용 됩니다.The resultSelector parameter is used to obtain a result value from each group and its key.

적용 대상

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

지정된 키 누적기 함수에 따라 시퀀스의 요소를 그룹화하고 각 그룹의 결과 값과 해당 키를 만듭니다.Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. 키는 지정된 비교자를 통해 비교됩니다.Keys are compared by using a specified comparer.

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

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

TResult

resultSelector에서 반환하는 결과 값의 형식입니다.The type of the result value returned by resultSelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

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

각 그룹의 결과 값을 만드는 함수입니다.A function to create a result value from each group.

comparer
IEqualityComparer<TKey>

키를 비교할 IEqualityComparer<T>입니다.An IEqualityComparer<T> to compare keys.

반환

IQueryable<TResult>

형식 인수가 TResult이고 각 요소가 그룹 및 해당 키에 대한 프로젝션을 나타내는 T:System.Linq.IQueryable`1입니다.An T:System.Linq.IQueryable`1 that has a type argument of TResult and where each element represents a projection over a group and its key.

예외

source, keySelector, resultSelector 또는 comparernull인 경우source or keySelector or resultSelector or comparer is null.

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) .The GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source keySelector 각 요소에 대해를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다.The expected behavior is that it groups the elements of source by key values that are obtained by invoking keySelector on each element. comparer매개 변수를 사용 하 여 키를 비교 하 고 resultSelector 매개 변수를 사용 하 여 각 그룹 및 해당 키에서 결과 값을 가져옵니다.The comparer parameter is used to compare keys and the resultSelector parameter is used to obtain a result value from each group and its key.

적용 대상

GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>)

지정된 키 선택기 함수에 따라 지정된 비교자로 키를 비교하여 시퀀스의 요소를 그룹화합니다.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::Linq::IQueryable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);
public static System.Linq.IQueryable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);
public static System.Linq.IQueryable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.IQueryable<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey)), comparer As IEqualityComparer(Of TKey)) As IQueryable(Of IGrouping(Of TKey, TSource))

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

comparer
IEqualityComparer<TKey>

키를 비교할 IEqualityComparer<T>입니다.An IEqualityComparer<T> to compare keys.

반환

IQueryable<IGrouping<TKey,TSource>>

IGrouping<TKey,TElement>에 개체 및 키의 시퀀스가 들어 있는 IQueryable<IGrouping<TKey, TSource>>(C#의 경우) 또는 IQueryable(Of IGrouping(Of TKey, TSource))(Visual Basic의 경우)입니다.An IQueryable<IGrouping<TKey, TSource>> in C# or IQueryable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> contains a sequence of objects and a key.

예외

source, keySelector 또는 comparernull인 경우source or keySelector or comparer is null.

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) .The GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source 키 값을 기준으로의 요소를 그룹화 하는 것입니다.The expected behavior is that it groups the elements of source by a key value. 키 값은 keySelector 각 요소에 대해를 호출 하 여 가져오며 키 값은를 사용 하 여 비교 됩니다 comparer .The key value is obtained by invoking keySelector on each element, and key values are compared by using comparer.

적용 대상

GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)

지정된 키 선택기 함수에 따라 시퀀스의 요소를 그룹화합니다.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::Linq::IQueryable<System::Linq::IGrouping<TKey, TSource> ^> ^ GroupBy(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, TKey> ^> ^ keySelector);
public static System.Linq.IQueryable<System.Linq.IGrouping<TKey,TSource>> GroupBy<TSource,TKey> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,TKey>> keySelector);
static member GroupBy : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, 'Key>> -> System.Linq.IQueryable<System.Linq.IGrouping<'Key, 'Source>>
<Extension()>
Public Function GroupBy(Of TSource, TKey) (source As IQueryable(Of TSource), keySelector As Expression(Of Func(Of TSource, TKey))) As IQueryable(Of IGrouping(Of TKey, TSource))

형식 매개 변수

TSource

source 요소의 형식입니다.The type of the elements of source.

TKey

keySelector에 지정된 함수가 반환하는 키 형식입니다.The type of the key returned by the function represented in keySelector.

매개 변수

source
IQueryable<TSource>

요소를 그룹화할 IQueryable<T>입니다.An IQueryable<T> whose elements to group.

keySelector
Expression<Func<TSource,TKey>>

각 요소에 대해 키를 추출하는 함수입니다.A function to extract the key for each element.

반환

IQueryable<IGrouping<TKey,TSource>>

IGrouping<TKey,TElement> 개체에 개체 및 키의 시퀀스가 들어 있는 IQueryable<IGrouping<TKey, TSource>>(C#의 경우) 또는 IQueryable(Of IGrouping(Of TKey, TSource))(Visual Basic의 경우)입니다.An IQueryable<IGrouping<TKey, TSource>> in C# or IQueryable(Of IGrouping(Of TKey, TSource)) in Visual Basic where each IGrouping<TKey,TElement> object contains a sequence of objects and a key.

예외

source 또는 keySelectornull인 경우source or keySelector is null.

예제

다음 코드 예제에서는를 사용 하 여 시퀀스의 요소를 그룹화 하는 방법을 보여 줍니다 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) .The following code example demonstrates how to use GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) to group the elements of a sequence.

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

public static void GroupByEx1()
{
    // Create a list of Pet objects.
    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 Pet.Age as the key.
    // Use Pet.Name as the value for each entry.
    var query = pets.AsQueryable().GroupBy(pet => pet.Age);

    // Iterate over each IGrouping in the collection.
    foreach (var ageGroup in query)
    {
        Console.WriteLine("Age group: {0}  Number of pets: {1}", ageGroup.Key, ageGroup.Count());
    }
}

/*
    This code produces the following output:

    Age group: 8  Number of pets: 1
    Age group: 4  Number of pets: 2
    Age group: 1  Number of pets: 1

*/

Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Shared 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 Pet.Age as the key.
    ' Use Pet.Name as the value for each entry.
    Dim query = pets.AsQueryable().GroupBy(Function(pet) pet.Age)

    Dim output As New System.Text.StringBuilder
    ' Iterate over each IGrouping in the collection.
    For Each ageGroup In query
        output.AppendFormat("Age group: {0}   Number of pets: {1}{2}", ageGroup.Key, ageGroup.Count(), vbCrLf)
    Next

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

' This code produces the following output:
'
' Age group: 8   Number of pets: 1
' Age group: 4   Number of pets: 2
' Age group: 1   Number of pets: 1

설명

이 메서드에 형식 인수가 형식 중 하나인 형식의 매개 변수가 하나 이상 있습니다 Expression<TDelegate> Func<T,TResult> .This method has at least one parameter of type Expression<TDelegate> whose type argument is one of the Func<T,TResult> types. 이러한 매개 변수는 람다 식을 전달할 수 있으며로 컴파일됩니다 Expression<TDelegate> .For these parameters, you can pass in a lambda expression and it will be compiled to an Expression<TDelegate>.

GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)메서드는 자신을 MethodCallExpression 생성 된 제네릭 메서드로 호출 하는을 생성 합니다 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) .The GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) method generates a MethodCallExpression that represents calling GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) itself as a constructed generic method. 그런 다음 MethodCallExpression CreateQuery<TElement>(Expression) IQueryProvider Provider 매개 변수의 속성이 나타내는의 메서드에를 전달 합니다 source .It then passes the MethodCallExpression to the CreateQuery<TElement>(Expression) method of the IQueryProvider represented by the Provider property of the source parameter.

호출을 나타내는 식 트리를 실행 한 결과로 발생 하는 쿼리 동작은 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 매개 변수의 형식 구현에 따라 달라 집니다 source .The query behavior that occurs as a result of executing an expression tree that represents calling GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) depends on the implementation of the type of the source parameter. 예상 되는 동작은 source 각 요소에서를 호출 하 여 가져온 키 값으로의 요소를 그룹화 하는 것입니다 keySelector .The expected behavior is that it groups the elements of source by a key value that is obtained by invoking keySelector on each element.

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