Queryable.GroupBy 方法

參考

定義

命名空間:: System.Linq

組件:: System.Linq.Queryable.dll

組件:: System.Core.dll

組件:: netstandard.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

群組序列的項目。

多載

GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>)	依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。索引鍵是使用指定的比較子來進行比較，而每個群組的項目則都是利用指定的函式進行投影。
GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>)	依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。每個群組的項目都是利用指定的函式進行投影。
GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>)	依據指定的索引鍵選取器函式來群組序列的項目，並使用指定的函式來投影每個群組的項目。
GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>)	使用指定的函式來群組序列的項目並投影每個群組的項目。索引鍵值是使用指定的比較子來進行比較。
GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>)	依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。
GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>)	依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。索引鍵是使用指定的比較子來進行比較。
GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>)	依據指定的索引鍵選擇器函式來群組序列的項目。
GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>)	依據指定的索引鍵選取器函式來群組序列的項目，並使用指定的比較子來比較索引鍵。

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。索引鍵是使用指定的比較子來進行比較，而每個群組的項目則都是利用指定的函式進行投影。

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)

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TElement

每個 IGrouping<TKey,TElement> 中的項目型別。

TResult

resultSelector 所傳回之結果值的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

elementSelector: Expression<Func<TSource,TElement>>

用來將每個來源項目對應至 IGrouping<TKey,TElement> 之項目的函式。

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

用來從各個群組建立結果值的函式。

comparer: IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>。

傳回

IQueryable<TResult>

T:System.Linq.IQueryable`1，其具有的型別自變數TResult，其中每個元素都代表群組及其索引鍵的投影。

例外狀況

ArgumentNullException

source、keySelector、elementSelector、resultSelector 或 comparer 為 null。

備註

這個方法至少有一個類型的參數，其類型 Expression<TDelegate> 自變數為其中一個型別 Func<T,TResult> 。針對這些參數，您可以傳入 Lambda 運算式，並將它編譯為 Expression<TDelegate>。

方法 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) 會產生， MethodCallExpression 表示呼叫 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) 本身為建構的泛型方法。然後，它會將傳遞給 MethodCallExpression CreateQuery<TElement>(Expression) 參數之屬性所Provider表示的方法IQueryProvidersource。

執行表示呼叫 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>, IEqualityComparer<TKey>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的實作 source 。預期的行為是它會依叫用keySelector每個元素取得的索引鍵值，將的專案source分組。參數 comparer 是用來比較索引鍵值。參數 elementSelector 是用來投影每個群組的專案，而 resultSelector 參數則用來從每個群組及其索引鍵取得結果值。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。每個群組的項目都是利用指定的函式進行投影。

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)

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TElement

每個 IGrouping<TKey,TElement> 中的項目型別。

TResult

resultSelector 所傳回之結果值的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

elementSelector: Expression<Func<TSource,TElement>>

用來將每個來源項目對應至 IGrouping<TKey,TElement> 之項目的函式。

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

用來從各個群組建立結果值的函式。

傳回

IQueryable<TResult>

T:System.Linq.IQueryable`1，其具有的型別自變數TResult，其中每個元素都代表群組及其索引鍵的投影。

例外狀況

ArgumentNullException

source、keySelector、elementSelector 或 resultSelector 為 null。

範例

下列程式代碼範例示範如何使用 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>) 將序列的專案分組，並投影類型的 TResult結果序列。

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

備註

方法 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>) 會產生， MethodCallExpression 表示呼叫 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>) 本身為建構的泛型方法。然後，它會將傳遞給 MethodCallExpression CreateQuery<TElement>(Expression) 參數之屬性所Provider表示的方法IQueryProvidersource。

執行表示呼叫 GroupBy<TSource,TKey,TElement,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TSource,TElement>>, Expression<Func<TKey, IEnumerable<TElement>,TResult>>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的實作 source 。預期的行為是它會依叫用keySelector每個元素取得的索引鍵值，將的專案source分組。參數 elementSelector 是用來投影每個群組的專案，而 resultSelector 參數則用來從每個群組及其索引鍵取得結果值。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並使用指定的函式來投影每個群組的項目。

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))

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TElement

每個 IGrouping<TKey,TElement> 中的項目型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

elementSelector: Expression<Func<TSource,TElement>>

用來將每個來源項目對應至 IGrouping<TKey,TElement> 之項目的函式。

傳回

IQueryable<IGrouping<TKey,TElement>>

C# 中的，或 IQueryable(Of IGrouping(Of TKey, TElement)) Visual Basic 中的，IQueryable<IGrouping<TKey, TElement>>其中每個IGrouping<TKey,TElement>物件都包含型TElement別和索引鍵的序列。

例外狀況

ArgumentNullException

source、keySelector 或 elementSelector 為 null。

範例

下列程式代碼範例示範如何使用 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) 來群組序列的專案。

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

備註

方法 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) 會產生， MethodCallExpression 表示呼叫 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) 本身為建構的泛型方法。然後，它會將傳遞給 MethodCallExpression CreateQuery<TElement>(Expression) 參數之屬性所Provider表示的方法IQueryProvidersource。

執行表示呼叫 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的實作 source 。預期的行為是它會依叫用每個元素取得keySelector的索引鍵值，將的專案source分組。它會在每個專案上叫 elementSelector 用，以取得結果專案。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

使用指定的函式來群組序列的項目並投影每個群組的項目。索引鍵值是使用指定的比較子來進行比較。

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))

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TElement

每個 IGrouping<TKey,TElement> 中的項目型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

elementSelector: Expression<Func<TSource,TElement>>

用來將每個來源項目對應至 IGrouping<TKey,TElement> 之項目的函式。

comparer: IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>。

傳回

IQueryable<IGrouping<TKey,TElement>>

例外狀況

ArgumentNullException

source、keySelector、elementSelector 或 comparer 為 null。

備註

方法 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) 會產生， MethodCallExpression 表示呼叫 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) 本身為建構的泛型方法。然後，它會將傳遞給 MethodCallExpression CreateQuery<TElement>(Expression) 參數之屬性所Provider表示的方法IQueryProvidersource。

執行表示呼叫 GroupBy<TSource,TKey,TElement>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TSource,TElement>>, IEqualityComparer<TKey>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的實作 source 。預期的行為是它會依叫用每個元素取得keySelector的索引鍵值，將的專案source分組。使用 comparer來比較索引鍵值。系統會 elementSelector 在每個專案上叫用參數，以取得結果專案。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。

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)

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TResult

resultSelector 所傳回之結果值的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

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

用來從各個群組建立結果值的函式。

傳回

IQueryable<TResult>

T:System.Linq.IQueryable`1，其類型自變數TResult為，其中每個元素代表群組及其索引鍵的投影。

例外狀況

ArgumentNullException

source、keySelector 或 resultSelector 為 null。

範例

下列程式代碼範例示範如何使用 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 來分組序列的專案，並投影類型 TResult的結果序列。

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

備註

這個方法至少有一個類型 Expression<TDelegate> 參數，其類型自變數為其中一個 Func<T,TResult> 型別。針對這些參數，您可以傳入 Lambda 運算式，並將它編譯為 Expression<TDelegate>。

方法 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 會產生， MethodCallExpression 表示 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 呼叫本身做為建構的泛型方法。然後，它會將傳遞MethodCallExpression至 CreateQuery<TElement>(Expression) 參數的屬性所Provider表示的 source 方法IQueryProvider。

執行表示呼叫 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的 source 實作。預期的行為是它會依叫用每個元素取得keySelector的索引鍵值，將的專案分組source。參數 resultSelector 可用來從每個群組及其索引鍵取得結果值。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並從每個群組及其索引鍵建立結果值。索引鍵是使用指定的比較子來進行比較。

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)

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

TResult

resultSelector 所傳回之結果值的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

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

用來從各個群組建立結果值的函式。

comparer: IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>。

傳回

IQueryable<TResult>

T:System.Linq.IQueryable`1，其類型自變數TResult為，其中每個元素代表群組及其索引鍵的投影。

例外狀況

ArgumentNullException

source、keySelector、resultSelector 或 comparer 為 null。

備註

方法 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) 會產生， MethodCallExpression 表示 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) 呼叫本身做為建構的泛型方法。然後，它會將傳遞MethodCallExpression至 CreateQuery<TElement>(Expression) 參數的屬性所Provider表示的 source 方法IQueryProvider。

執行表示呼叫 GroupBy<TSource,TKey,TResult>(IQueryable<TSource>, Expression<Func<TSource, TKey>>, Expression<Func<TKey,IEnumerable<TSource>,TResult>>, IEqualityComparer<TKey>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的 source 實作。預期的行為是它會依每個元素叫用取得keySelector的索引鍵值，將的專案分組source。參數 comparer 是用來比較索引鍵， resultSelector 而參數是用來從每個群組及其索引鍵取得結果值。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選擇器函式來群組序列的項目。

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))

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

傳回

IQueryable<IGrouping<TKey,TSource>>

C# 或 IQueryable(Of IGrouping(Of TKey, TSource)) Visual Basic 中的，IQueryable<IGrouping<TKey, TSource>>其中每個IGrouping<TKey,TElement>物件都包含一連串的物件和索引鍵。

例外狀況

ArgumentNullException

source 或 keySelector 為 null。

範例

下列程式代碼範例示範如何使用 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 來分組序列的專案。

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

備註

方法 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 會產生， MethodCallExpression 表示 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 呼叫本身做為建構的泛型方法。然後，它會將傳遞MethodCallExpression至 CreateQuery<TElement>(Expression) 參數的屬性所Provider表示的 source 方法IQueryProvider。

執行表示呼叫 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的 source 實作。預期的行為是它會依叫用每個元素取得keySelector的索引鍵值，將的專案分組source。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

來源:: Queryable.cs

依據指定的索引鍵選取器函式來群組序列的項目，並使用指定的比較子來比較索引鍵。

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))

類型參數

TSource

source 項目的類型。

TKey

keySelector 中表示之函式所傳回索引鍵的型別。

參數

source: IQueryable<TSource>

要群組其項目的 IQueryable<T>。

keySelector: Expression<Func<TSource,TKey>>

用來擷取各項目之索引鍵的函式。

comparer: IEqualityComparer<TKey>

用來比較金鑰的 IEqualityComparer<T>。

傳回

IQueryable<IGrouping<TKey,TSource>>

C# 中的， IQueryable<IGrouping<TKey, TSource>> 或 IQueryable(Of IGrouping(Of TKey, TSource)) Visual Basic 中的，其中每個 IGrouping<TKey,TElement> 物件和索引鍵都包含一連串的物件和索引鍵。

例外狀況

ArgumentNullException

source、keySelector 或 comparer 為 null。

備註

方法 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) 會產生， MethodCallExpression 表示 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) 呼叫本身做為建構的泛型方法。然後，它會將傳遞MethodCallExpression至 CreateQuery<TElement>(Expression) 參數的屬性所Provider表示的 source 方法IQueryProvider。

執行表示呼叫 GroupBy<TSource,TKey>(IQueryable<TSource>, Expression<Func<TSource,TKey>>, IEqualityComparer<TKey>) 的表達式樹狀結構所產生的查詢行為，取決於參數類型的 source 實作。預期的行為是它會依索引鍵值將的專案 source 分組。藉由叫 keySelector 用每個元素來取得索引鍵值，並使用來比較 comparer索引鍵值。

適用於

共用方式為

Queryable.GroupBy 方法

定義

多載

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

類型參數

參數

傳回

例外狀況

備註

適用於

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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

類型參數

參數

傳回

例外狀況

備註

適用於

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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

類型參數

參數

傳回

例外狀況

備註

適用於

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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

類型參數

參數

傳回

例外狀況

備註

適用於

其他資源