Queryable.Join 方法

定義

命名空間:

System.Linq

組件:

netstandard.dll, System.Linq.Queryable.dll

根據匹配的鍵數關聯兩個序列的元素。

多載

名稱	Description
Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,TInner,TResult>>)	根據匹配的鍵數關聯兩個序列的元素。 默認相等比較子可用來比較索引鍵。
Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,TInner,TResult>>, IEqualityComparer<TKey>)	根據匹配的鍵數關聯兩個序列的元素。 指定的 IEqualityComparer<T> 可用來比較索引鍵。

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

來源:

Queryable.cs

根據匹配的鍵數關聯兩個序列的元素。 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> ^ Join(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, TInner, TResult> ^> ^ resultSelector);

public static System.Linq.IQueryable<TResult> Join<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,TInner,TResult>> resultSelector);

static member Join : 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, 'Inner, 'Result>> -> System.Linq.IQueryable<'Result>

<Extension()>
Public Function Join(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, 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,TInner,TResult>>

一個用來從兩個匹配元素建立結果元素的函式。

傳回

IQueryable<TResult>

一個 IQueryable<T> 的元素 TResult 是透過對兩個序列進行內聯而得到的。

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根據 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,TInner,TResult>>) 共同鍵數執行兩個序列的內部連接。

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

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

public static void JoinEx1()
{
    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 };

    // Join the list of Person objects and the list of Pet objects
    // to create a list of person-pet pairs where each element is
    // an anonymous type that contains the name of pet and the name
    // of the person that owns the pet.
    var query = people.AsQueryable().Join(pets,
                    person => person,
                    pet => pet.Owner,
                    (person, pet) =>
                        new { OwnerName = person.Name, Pet = pet.Name });

    foreach (var obj in query)
    {
        Console.WriteLine(
            "{0} - {1}",
            obj.OwnerName,
            obj.Pet);
    }
}

/*
    This code produces the following output:

    Hedlund, Magnus - Daisy
    Adams, Terry - Barley
    Adams, Terry - 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 JoinEx1()
    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})

    ' Join the list of Person objects and the list of Pet objects 
    ' to create a list of person-pet pairs where each element is 
    ' an anonymous type that contains pet's name and the name of the
    ' Person object that owns the pet.
    Dim query = people.AsQueryable().Join(pets, _
                    Function(person) person, _
                    Function(pet) pet.Owner, _
                    Function(person, pet) _
                        New With {.OwnerName = person.Name, .Pet = pet.Name})

    Dim output As New System.Text.StringBuilder
    For Each obj In query
        output.AppendLine(String.Format( _
            "{0} - {1}", obj.OwnerName, obj.Pet))
    Next

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

' This code produces the following output:

' Hedlund, Magnus - Daisy
' Adams, Terry - Barley
' Adams, Terry - 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 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,TInner,TResult>>) 方法產生的 是 MethodCallExpression ，代表 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,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 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,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。 預期的行為是內在結合的行為。 outerKeySelector innerKeySelector與函數分別用於從outer與 inner中提取鍵數。 這些鍵會被比較以匹配每個序列中的元素。 每個元素會儲存 inner 一對元素，該元素與 中的 outer元素相匹配。 接著會呼叫該 resultSelector 函式，從每對匹配元素中投射出一個結果物件。

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

來源:

Queryable.cs

根據匹配的鍵數關聯兩個序列的元素。 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> ^ Join(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, TInner, TResult> ^> ^ resultSelector, System::Collections::Generic::IEqualityComparer<TKey> ^ comparer);

public static System.Linq.IQueryable<TResult> Join<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,TInner,TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer);

static member Join : 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, 'Inner, 'Result>> * System.Collections.Generic.IEqualityComparer<'Key> -> System.Linq.IQueryable<'Result>

<Extension()>
Public Function Join(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, 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,TInner,TResult>>

一個用來從兩個匹配元素建立結果元素的函式。

comparer

IEqualityComparer<TKey>

An IEqualityComparer<T> 用來雜湊和比較金鑰。

傳回

IQueryable<TResult>

一個 IQueryable<T> 的元素 TResult 是透過對兩個序列進行內聯而得到的。

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 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,TInner,TResult>>, IEqualityComparer<TKey>) 方法產生的 是 MethodCallExpression ，代表 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,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 Join<TOuter,TInner,TKey,TResult>(IQueryable<TOuter>, IEnumerable<TInner>, Expression<Func<TOuter,TKey>>, Expression<Func<TInner,TKey>>, Expression<Func<TOuter,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。 預期的行為是內在結合的行為。 outerKeySelector innerKeySelector與函數分別用於從outer與 inner中提取鍵數。 這些鍵可透過使用 comparer進行比較以求相等。 比較結果用來為每個元素建立一對匹配，該配 inner 對與 中的 outer元素相符。 接著會呼叫該 resultSelector 函式，從每對匹配元素中投射出一個結果物件。