Queryable.GroupJoin 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。

根據索引鍵相等與否，將兩個序列的項目相互關聯，並群組產生的結果。

多載

GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>)	根據索引鍵相等與否，將兩個序列的項目相互關聯，並群組產生的結果。預設的相等比較子是用於比較索引鍵。
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>)	根據索引鍵相等與否，將兩個序列的項目相互關聯，並群組產生的結果。指定的 IEqualityComparer<T> 是用於比較索引鍵。

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

來源:: Queryable.cs

來源:: Queryable.cs

根據索引鍵相等與否，將兩個序列的項目相互關聯，並群組產生的結果。預設的相等比較子是用於比較索引鍵。

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

第一個序列之項目的類型。

TInner

第二個序列之項目的類型。

TKey

索引鍵選取器函式所傳回之索引鍵的類型。

TResult

結果項目的類型。

參數

outer: IQueryable<TOuter>

要聯結的第一個序列。

inner: IEnumerable<TInner>

要加入第一個序列的序列。

outerKeySelector: Expression<Func<TOuter,TKey>>

用來從第一個序列各個項目擷取聯結索引鍵的函式。

innerKeySelector: Expression<Func<TInner,TKey>>

用來從第二個序列各個項目擷取聯結索引鍵的函式。

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

函式，用來從第一個序列的項目以及第二個序列的相符項目集合建立結果項目。

傳回

IQueryable<TResult>

IQueryable<T>，其中包含透過對兩個序列執行群組聯結所取得之型別 TResult 的項目。

例外狀況

ArgumentNullException

outer、inner、outerKeySelector、innerKeySelector 或 resultSelector 為 null。

範例

下列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>>) 在兩個序列上執行群組聯結。

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

這個方法至少有一個類型 Expression<TDelegate> 參數，其類型引數為其中一個 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 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 會產生， MethodCallExpression 表示 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 outer 方法 IQueryProvider 。

執行表示呼叫 GroupJoin<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,IEnumerable<TInner>,TResult>>) 的運算式樹狀結構所產生的查詢行為，取決於參數類型的 outer 實作。預期的行為是 outerKeySelector 和 innerKeySelector 函式分別用來從 outer 和 inner 擷取索引鍵。這些索引鍵會比較是否相等，以比對中每個元素與中的 outer 零個或多個專案 inner 。然後，會叫用函 resultSelector 式來投影每個相互關聯專案群組的結果物件。

適用於

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

來源:: Queryable.cs

來源:: Queryable.cs

根據索引鍵相等與否，將兩個序列的項目相互關聯，並群組產生的結果。指定的 IEqualityComparer<T> 是用於比較索引鍵。

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);

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

第一個序列之項目的類型。

TInner

第二個序列之項目的類型。

TKey

索引鍵選取器函式所傳回之索引鍵的類型。

TResult

結果項目的類型。

參數

outer: IQueryable<TOuter>

要聯結的第一個序列。

inner: IEnumerable<TInner>

要加入第一個序列的序列。

outerKeySelector: Expression<Func<TOuter,TKey>>

用來從第一個序列各個項目擷取聯結索引鍵的函式。

innerKeySelector: Expression<Func<TInner,TKey>>

用來從第二個序列各個項目擷取聯結索引鍵的函式。

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

函式，用來從第一個序列的項目以及第二個序列的相符項目集合建立結果項目。

comparer: IEqualityComparer<TKey>

用來雜湊及比較索引鍵的比較子。

傳回

IQueryable<TResult>

IQueryable<T>，其中包含透過對兩個序列執行群組聯結所取得之型別 TResult 的項目。

例外狀況

ArgumentNullException

outer、inner、outerKeySelector、innerKeySelector 或 resultSelector 為 null。

備註

方法 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>) 會產生， MethodCallExpression 表示 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 outer 方法 IQueryProvider 。

執行表示呼叫 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>) 的運算式樹狀結構所產生的查詢行為，取決於參數類型的 outer 實作。預期的行為是 outerKeySelector 和 innerKeySelector 函式分別用來從 outer 和 inner 擷取索引鍵。使用來比較這些索引鍵是否相等 comparer 。比較的結果是用來比對中每個元素與中 outer 零個或多個元素。 inner 然後，會叫用函 resultSelector 式來投影每個相互關聯專案群組的結果物件。

適用於

Queryable.GroupJoin 方法

定義

多載

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

類型參數

參數

傳回

例外狀況

範例

備註

適用於

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>)

類型參數

參數

傳回

例外狀況

備註

適用於

意見反應

其他資源