Enumerable.Join Metoda

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

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

static member Join : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> -> seq<'Result>

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

Parametry typu

Parametry

Návraty

IEnumerable<TResult>

IEnumerable<T>Obsahuje prvky typu TResult , které jsou získány prostřednictvím vnitřního spojení ve dvou sekvencích.An IEnumerable<T> that has elements of type TResult that are obtained by performing an inner join on two sequences.

Výjimky

Příklady

Následující příklad kódu ukazuje, jak použít Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) k provedení vnitřního spojení dvou sekvencí založených na společném klíči.The following code example demonstrates how to use Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>) to perform an inner join of two sequences based on a common key.

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 };

    // Create a list of Person-Pet pairs where
    // each element is an anonymous type that contains a
    // Pet's name and the name of the Person that owns the Pet.
    var query =
        people.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

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})

    ' Create a list of Person-Pet pairs, where each element is an
    ' anonymous type that contains a Pet's name and the name of the 
    ' Person that owns the Pet.
    Dim query =
people.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(obj.OwnerName & " - " & obj.Pet)
    Next

    ' Display the output.
    Console.WriteLine(output.ToString)
End Sub

' This code produces the following output:
'
' Hedlund, Magnus - Daisy
' Adams, Terry - Barley
' Adams, Terry - Boots
' Weiss, Charlotte - Whiskers

Poznámky

Tato metoda je implementována pomocí odloženého provedení.This method is implemented by using deferred execution. Okamžitá návratová hodnota je objekt, který ukládá všechny informace, které jsou požadovány k provedení této akce.The immediate return value is an object that stores all the information that is required to perform the action. Dotaz reprezentovaný touto metodou není proveden, dokud se nevytvoří výčet objektu buď voláním GetEnumerator metody přímo nebo pomocí foreach jazyka Visual C# nebo For Each Visual Basic.The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

Výchozí porovnávání rovnosti Default je použito pro hodnoty hash a Compare.The default equality comparer, Default, is used to hash and compare keys.

Spojení odkazuje na operaci korelující prvky dvou zdrojů informací, které jsou založeny na společném klíči.A join refers to the operation of correlating the elements of two sources of information based on a common key. Join přiřadí dva zdroje informací a klíče, pomocí kterých jsou vzájemně spárovány v jednom volání metody.Join brings the two information sources and the keys by which they are matched together in one method call. To se liší od použití SelectMany , což vyžaduje více než jedno volání metody pro provedení stejné operace.This differs from the use of SelectMany, which requires more than one method call to perform the same operation.

Join zachovává pořadí prvků v outer a pro každý z těchto prvků pořadím, v němž se shodují prvky inner .Join preserves the order of the elements of outer, and for each of these elements, the order of the matching elements of inner.

V syntaxi výrazu dotazu je join klauzule (Visual C#) nebo Join (Visual Basic) přeložena k vyvolání Join .In query expression syntax, a join (Visual C#) or Join (Visual Basic) clause translates to an invocation of Join.

V rámci podmínek relační databáze Join metoda implementuje vnitřní equijoin.In relational database terms, the Join method implements an inner equijoin. ' Inner ' znamená, že do výsledků jsou zahrnuty pouze prvky, které mají shodu ve druhé sekvenci.'Inner' means that only elements that have a match in the other sequence are included in the results. "Equijoin" je spojení, ve kterém jsou klíče porovnány s rovností.An 'equijoin' is a join in which the keys are compared for equality. Levá operace vnějšího spojení neobsahuje žádný vyhrazený standardní operátor dotazu, ale lze ji provést pomocí GroupJoin metody.A left outer join operation has no dedicated standard query operator, but can be performed by using the GroupJoin method. Viz operace join.See Join Operations.

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

public static System.Collections.Generic.IEnumerable<TResult> Join<TOuter,TInner,TKey,TResult> (this System.Collections.Generic.IEnumerable<TOuter> outer, System.Collections.Generic.IEnumerable<TInner> inner, Func<TOuter,TKey> outerKeySelector, Func<TInner,TKey> innerKeySelector, Func<TOuter,TInner,TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey> comparer);

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

static member Join : seq<'Outer> * seq<'Inner> * Func<'Outer, 'Key> * Func<'Inner, 'Key> * Func<'Outer, 'Inner, 'Result> * System.Collections.Generic.IEqualityComparer<'Key> -> seq<'Result>

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

Parametry typu

Parametry

Návraty

IEnumerable<TResult>

IEnumerable<T>Obsahuje prvky typu TResult , které jsou získány prostřednictvím vnitřního spojení ve dvou sekvencích.An IEnumerable<T> that has elements of type TResult that are obtained by performing an inner join on two sequences.

Výjimky

Poznámky

Tato metoda je implementována pomocí odloženého provedení.This method is implemented by using deferred execution. Okamžitá návratová hodnota je objekt, který ukládá všechny informace, které jsou požadovány k provedení této akce.The immediate return value is an object that stores all the information that is required to perform the action. Dotaz reprezentovaný touto metodou není proveden, dokud se nevytvoří výčet objektu buď voláním GetEnumerator metody přímo nebo pomocí foreach jazyka Visual C# nebo For Each Visual Basic.The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in Visual C# or For Each in Visual Basic.

Pokud comparer je null , použije se výchozí srovnávací porovnávání rovnosti Default klíčů a hodnot hash a Compare.If comparer is null, the default equality comparer, Default, is used to hash and compare keys.

Spojení odkazuje na operaci korelující prvky dvou zdrojů informací, které jsou založeny na společném klíči.A join refers to the operation of correlating the elements of two sources of information based on a common key. Join přiřadí dva zdroje informací a klíče, pomocí kterých jsou vzájemně spárovány v jednom volání metody.Join brings the two information sources and the keys by which they are matched together in one method call. To se liší od použití SelectMany , což vyžaduje více než jedno volání metody pro provedení stejné operace.This differs from the use of SelectMany, which requires more than one method call to perform the same operation.

Join zachovává pořadí prvků v outer a pro každý z těchto prvků pořadím, v němž se shodují prvky inner .Join preserves the order of the elements of outer, and for each of these elements, the order of the matching elements of inner.

V rámci podmínek relační databáze Join metoda implementuje vnitřní equijoin.In relational database terms, the Join method implements an inner equijoin. ' Inner ' znamená, že do výsledků jsou zahrnuty pouze prvky, které mají shodu ve druhé sekvenci.'Inner' means that only elements that have a match in the other sequence are included in the results. "Equijoin" je spojení, ve kterém jsou klíče porovnány s rovností.An 'equijoin' is a join in which the keys are compared for equality. Levá operace vnějšího spojení neobsahuje žádný vyhrazený standardní operátor dotazu, ale lze ji provést pomocí GroupJoin metody.A left outer join operation has no dedicated standard query operator, but can be performed by using the GroupJoin method. Viz operace join.See Join Operations.