Queryable.GroupJoin 方法

定義

命名空間:

System.Linq

組件:

netstandard.dll, System.Linq.Queryable.dll

根據索引鍵相等將兩個序列的專案相互關聯，並將結果分組。

多載

名稱	Description
GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>)	根據索引鍵相等將兩個序列的專案相互關聯，並將結果分組。 默認相等比較子可用來比較索引鍵。
GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>, IEqualityComparer<TKey>)	根據索引鍵相等將兩個序列的專案相互關聯，並將結果分組。 指定的 IEqualityComparer<T> 可用來比較索引鍵。

GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>)

來源:

Queryable.cs

根據索引鍵相等將兩個序列的專案相互關聯，並將結果分組。 默認相等比較子可用來比較索引鍵。

public:
generic <typename TOuter, typename TInner, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IQueryable<TResult> ^ GroupJoin(System::Linq::IQueryable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, System::Linq::Expressions::Expression<Func<TOuter, TKey> ^> ^ outerKeySelector, System::Linq::Expressions::Expression<Func<TInner, TKey> ^> ^ innerKeySelector, System::Linq::Expressions::Expression<Func<TOuter, System::Collections::Generic::IEnumerable<TInner> ^, TResult> ^> ^ resultSelector);

public static System.Linq.IQueryable<TResult> GroupJoin<TOuter,TInner,TKey,TResult>(this System.Linq.IQueryable<TOuter> outer, System.Collections.Generic.IEnumerable<TInner> inner, System.Linq.Expressions.Expression<Func<TOuter,TKey>> outerKeySelector, System.Linq.Expressions.Expression<Func<TInner,TKey>> innerKeySelector, System.Linq.Expressions.Expression<Func<TOuter,System.Collections.Generic.IEnumerable<TInner>,TResult>> resultSelector);

static member GroupJoin : System.Linq.IQueryable<'Outer> * seq<'Inner> * System.Linq.Expressions.Expression<Func<'Outer, 'Key>> * System.Linq.Expressions.Expression<Func<'Inner, 'Key>> * System.Linq.Expressions.Expression<Func<'Outer, seq<'Inner>, 'Result>> -> System.Linq.IQueryable<'Result>

<Extension()>
Public Function GroupJoin(Of TOuter, TInner, TKey, TResult) (outer As IQueryable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Expression(Of Func(Of TOuter, TKey)), innerKeySelector As Expression(Of Func(Of TInner, TKey)), resultSelector As Expression(Of Func(Of TOuter, IEnumerable(Of TInner), TResult))) As IQueryable(Of TResult)

類型參數

TOuter

第一個序列元素的類型。

TInner

第二序列元素的類型。

TKey

鍵選擇器功能回傳的鍵型。

TResult

結果元素的類型。

參數

outer

IQueryable<TOuter>

第一個加入的序列。

inner

IEnumerable<TInner>

將序列連接到第一個序列。

outerKeySelector

Expression<Func<TOuter,TKey>>

一個用來從第一個序列中每個元素提取連接鍵的函式。

innerKeySelector

Expression<Func<TInner,TKey>>

一個用來從第二個序列中每個元素提取連接鍵的函式。

resultSelector

Expression<Func<TOuter,IEnumerable<TInner>,TResult>>

一個函式，用來從第一個序列中的一個元素和第二個序列中一組相符的元素組成結果元素。

傳回

IQueryable<TResult>

一個 IQueryable<T> 包含由對兩個序列進行分組連接而得到的類型 TResult 元素。

例外狀況

ArgumentNullException

outer或、inner或outerKeySelectorinnerKeySelectorresultSelector是。null

範例

以下程式碼範例示範如何使用 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 該序列進行分組連接。

class Person
{
    public string Name { get; set; }
}

class Pet
{
    public string Name { get; set; }
    public Person Owner { get; set; }
}

public static void GroupJoinEx1()
{
    Person magnus = new Person { Name = "Hedlund, Magnus" };
    Person terry = new Person { Name = "Adams, Terry" };
    Person charlotte = new Person { Name = "Weiss, Charlotte" };

    Pet barley = new Pet { Name = "Barley", Owner = terry };
    Pet boots = new Pet { Name = "Boots", Owner = terry };
    Pet whiskers = new Pet { Name = "Whiskers", Owner = charlotte };
    Pet daisy = new Pet { Name = "Daisy", Owner = magnus };

    List<Person> people = new List<Person> { magnus, terry, charlotte };
    List<Pet> pets = new List<Pet> { barley, boots, whiskers, daisy };

    // Create a list where each element is an anonymous
    // type that contains a person's name and a collection
    // of names of the pets that are owned by them.
    var query =
        people.AsQueryable().GroupJoin(pets,
                         person => person,
                         pet => pet.Owner,
                         (person, petCollection) =>
                             new
                             {
                                 OwnerName = person.Name,
                                 Pets = petCollection.Select(pet => pet.Name)
                             });

    foreach (var obj in query)
    {
        // Output the owner's name.
        Console.WriteLine("{0}:", obj.OwnerName);
        // Output each of the owner's pet's names.
        foreach (string pet in obj.Pets)
            Console.WriteLine("  {0}", pet);
    }
}

/*
    This code produces the following output:

    Hedlund, Magnus:
      Daisy
    Adams, Terry:
      Barley
      Boots
    Weiss, Charlotte:
      Whiskers
*/

Structure Person
    Public Name As String
End Structure

Structure Pet
    Public Name As String
    Public Owner As Person
End Structure

Shared Sub GroupJoinEx1()
    Dim magnus As New Person With {.Name = "Hedlund, Magnus"}
    Dim terry As New Person With {.Name = "Adams, Terry"}
    Dim charlotte As New Person With {.Name = "Weiss, Charlotte"}

    Dim barley As New Pet With {.Name = "Barley", .Owner = terry}
    Dim boots As New Pet With {.Name = "Boots", .Owner = terry}
    Dim whiskers As New Pet With {.Name = "Whiskers", .Owner = charlotte}
    Dim daisy As New Pet With {.Name = "Daisy", .Owner = magnus}

    Dim people As New List(Of Person)(New Person() {magnus, terry, charlotte})
    Dim pets As New List(Of Pet)(New Pet() {barley, boots, whiskers, daisy})

    ' Create a list where each element is an anonymous 
    ' type that contains a person's name and a collection
    ' of the names of the pets that are owned by them.
    Dim query = _
        people.AsQueryable().GroupJoin(pets, _
                   Function(person) person, _
                   Function(pet) pet.Owner, _
                   Function(person, petCollection) _
                       New With {.OwnerName = person.Name, _
                                 .Pets = petCollection.Select( _
                                                    Function(pet) pet.Name)})

    Dim output As New System.Text.StringBuilder
    For Each obj In query
        ' Output the owner's name.
        output.AppendLine(String.Format("{0}:", obj.OwnerName))
        ' Output each of the owner's pet's names.
        For Each pet As String In obj.Pets
            output.AppendLine(String.Format("  {0}", pet))
        Next
    Next

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

' This code produces the following output:

' Hedlund, Magnus:
'   Daisy
' Adams, Terry:
'   Barley
'   Boots
' Weiss, Charlotte:
'   Whiskers

備註

此方法至少有一個型別 Expression<TDelegate> 參數，其型別參數的參數是其中一個 Func<T,TResult> 型別。 對於這些參數，你可以輸入 lambda 運算式，然後它會被編譯成 Expression<TDelegate>。

該 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 方法產生的 是 MethodCallExpression ，代表 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 呼叫本身為一個構造化的泛型方法。 接著將 傳遞MethodCallExpression給CreateQuery<TElement>(Expression)IQueryProvider由參數Provider性質outer所表示的方法。

執行代表呼叫 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 的表達式樹所產生的查詢行為，取決於參數型別 outer 的實作。 預期行為是 outerKeySelector 和 innerKeySelector 函數分別用來從 和 inner中提取鍵。outer 這些鍵會被比較以使 中的 outer 每個元素與 中 inner零個或多個元素相等。 接著會呼叫該 resultSelector 函式，從每個相關元素群組中投影一個結果物件。

GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>, IEqualityComparer<TKey>)

來源:

Queryable.cs

根據索引鍵相等將兩個序列的專案相互關聯，並將結果分組。 指定的 IEqualityComparer<T> 可用來比較索引鍵。

public:
generic <typename TOuter, typename TInner, typename TKey, typename TResult>
[System::Runtime::CompilerServices::Extension]
 static System::Linq::IQueryable<TResult> ^ GroupJoin(System::Linq::IQueryable<TOuter> ^ outer, System::Collections::Generic::IEnumerable<TInner> ^ inner, System::Linq::Expressions::Expression<Func<TOuter, TKey> ^> ^ outerKeySelector, System::Linq::Expressions::Expression<Func<TInner, TKey> ^> ^ innerKeySelector, System::Linq::Expressions::Expression<Func<TOuter, System::Collections::Generic::IEnumerable<TInner> ^, TResult> ^> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);

public static System.Linq.IQueryable<TResult> GroupJoin<TOuter,TInner,TKey,TResult>(this System.Linq.IQueryable<TOuter> outer, System.Collections.Generic.IEnumerable<TInner> inner, System.Linq.Expressions.Expression<Func<TOuter,TKey>> outerKeySelector, System.Linq.Expressions.Expression<Func<TInner,TKey>> innerKeySelector, System.Linq.Expressions.Expression<Func<TOuter,System.Collections.Generic.IEnumerable<TInner>,TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);

static member GroupJoin : System.Linq.IQueryable<'Outer> * seq<'Inner> * System.Linq.Expressions.Expression<Func<'Outer, 'Key>> * System.Linq.Expressions.Expression<Func<'Inner, 'Key>> * System.Linq.Expressions.Expression<Func<'Outer, seq<'Inner>, 'Result>> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.IQueryable<'Result>

<Extension()>
Public Function GroupJoin(Of TOuter, TInner, TKey, TResult) (outer As IQueryable(Of TOuter), inner As IEnumerable(Of TInner), outerKeySelector As Expression(Of Func(Of TOuter, TKey)), innerKeySelector As Expression(Of Func(Of TInner, TKey)), resultSelector As Expression(Of Func(Of TOuter, IEnumerable(Of TInner), TResult)), comparer As IEqualityComparer(Of TKey)) As IQueryable(Of TResult)

類型參數

TOuter

第一個序列元素的類型。

TInner

第二序列元素的類型。

TKey

鍵選擇器功能回傳的鍵型。

TResult

結果元素的類型。

參數

outer

IQueryable<TOuter>

第一個加入的序列。

inner

IEnumerable<TInner>

將序列連接到第一個序列。

outerKeySelector

Expression<Func<TOuter,TKey>>

一個用來從第一個序列中每個元素提取連接鍵的函式。

innerKeySelector

Expression<Func<TInner,TKey>>

一個用來從第二個序列中每個元素提取連接鍵的函式。

resultSelector

Expression<Func<TOuter,IEnumerable<TInner>,TResult>>

一個函式，用來從第一個序列中的一個元素和第二個序列中一組相符的元素組成結果元素。

comparer

IEqualityComparer<TKey>

一個比較雜湊值和比較鍵的工具。

傳回

IQueryable<TResult>

一個 IQueryable<T> 包含由對兩個序列進行分組連接而得到的類型 TResult 元素。

例外狀況

ArgumentNullException

outer或、inner或outerKeySelectorinnerKeySelectorresultSelector是。null

備註

此方法至少有一個型別 Expression<TDelegate> 參數，其型別參數的參數是其中一個 Func<T,TResult> 型別。 對於這些參數，你可以輸入 lambda 運算式，然後它會被編譯成 Expression<TDelegate>。

該 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>, IEqualityComparer<TKey>) 方法產生的 是 MethodCallExpression ，代表 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>, IEqualityComparer<TKey>) 呼叫本身為一個構造化的泛型方法。 接著將 傳遞MethodCallExpression給CreateQuery<TElement>(Expression)IQueryProvider由參數Provider性質outer所表示的方法。

執行代表呼叫 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>, IEqualityComparer<TKey>) 的表達式樹所產生的查詢行為，取決於參數型別 outer 的實作。 預期行為是 outerKeySelector 和 innerKeySelector 函數分別用來從 和 inner中提取鍵。outer 這些鍵可透過使用 comparer進行比較以求相等。 比較結果用來將 中的outer每個元素與 中零個或多個元素匹配。inner 接著會呼叫該 resultSelector 函式，從每個相關元素群組中投影一個結果物件。