Queryable.All<TSource> Metoda

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool All(System::Linq::IQueryable<TSource> ^ source, System::Linq::Expressions::Expression<Func<TSource, bool> ^> ^ predicate);

public static bool All<TSource> (this System.Linq.IQueryable<TSource> source, System.Linq.Expressions.Expression<Func<TSource,bool>> predicate);

static member All : System.Linq.IQueryable<'Source> * System.Linq.Expressions.Expression<Func<'Source, bool>> -> bool

<Extension()>
Public Function All(Of TSource) (source As IQueryable(Of TSource), predicate As Expression(Of Func(Of TSource, Boolean))) As Boolean

Parametry typu

Parametry

Návraty

truejestliže každý prvek zdrojové sekvence projde testem v zadaném predikátu nebo pokud je posloupnost prázdná; v opačném případě . false

Výjimky

Příklady

Následující příklad kódu ukazuje, jak použít All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) k určení, zda všechny prvky v sekvenci splňují podmínku.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void AllEx1()
{
    // Create an array of Pets.
    Pet[] pets = { new Pet { Name="Barley", Age=10 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=6 } };

    // Determine whether all pet names in the array start with 'B'.
    bool allStartWithB =
        pets.AsQueryable().All(pet => pet.Name.StartsWith("B"));

    Console.WriteLine(
        "{0} pet names start with 'B'.",
        allStartWithB ? "All" : "Not all");
}

// This code produces the following output:
//
//  Not all pet names start with 'B'.

Sub AllEx()
    ' Create an array of Pets.
    Dim pets() As Pet = _
        {New Pet With {.Name = "Barley", .Age = 10}, _
         New Pet With {.Name = "Boots", .Age = 4}, _
         New Pet With {.Name = "Whiskers", .Age = 6}}

    ' Determine whether all pet names in the array start with 'B'.
    Dim allStartWithB As Boolean = _
        pets.AsQueryable().All(Function(ByVal pet) pet.Name.StartsWith("B"))

    MsgBox(String.Format( _
        "{0} pet names start with 'B'.", _
        IIf(allStartWithB, "All", "Not all")))
End Sub

Public Structure Pet
    Dim Name As String
    Dim Age As Integer
End Structure

' This code produces the following output:
'
'  Not all pet names start with 'B'.

Logická hodnota, kterou metoda vrací, All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) se obvykle používá v predikátu where klauzule (Where klauzule v jazyce Visual Basic) nebo v přímém volání Where metody. Následující příklad ukazuje toto použití All metody.

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}
class Person
{
    public string LastName { get; set; }
    public Pet[] Pets { get; set; }
}

public static void AllEx2()
{
    List<Person> people = new List<Person>
        { new Person { LastName = "Haas",
                       Pets = new Pet[] { new Pet { Name="Barley", Age=10 },
                                          new Pet { Name="Boots", Age=14 },
                                          new Pet { Name="Whiskers", Age=6 }}},
          new Person { LastName = "Fakhouri",
                       Pets = new Pet[] { new Pet { Name = "Snowball", Age = 1}}},
          new Person { LastName = "Antebi",
                       Pets = new Pet[] { new Pet { Name = "Belle", Age = 8} }},
          new Person { LastName = "Philips",
                       Pets = new Pet[] { new Pet { Name = "Sweetie", Age = 2},
                                          new Pet { Name = "Rover", Age = 13}} }
        };

    // Determine which people have pets that are all older than 5.
    IEnumerable<string> names = from person in people
                                where person.Pets.AsQueryable().All(pet => pet.Age > 5)
                                select person.LastName;

    foreach (string name in names)
        Console.WriteLine(name);

    /* This code produces the following output:
     *
     * Haas
     * Antebi
     */
}

Structure Pet
    Public Name As String
    Public Age As Integer
End Structure

Structure Person
    Public LastName As String
    Public Pets() As Pet
End Structure

Sub AllEx2()
    Dim people As New List(Of Person)(New Person() _
        {New Person With {.LastName = "Haas", _
                          .Pets = New Pet() {New Pet With {.Name = "Barley", .Age = 10}, _
                                             New Pet With {.Name = "Boots", .Age = 14}, _
                                             New Pet With {.Name = "Whiskers", .Age = 6}}}, _
          New Person With {.LastName = "Fakhouri", _
                           .Pets = New Pet() {New Pet With {.Name = "Snowball", .Age = 1}}}, _
          New Person With {.LastName = "Antebi", _
                           .Pets = New Pet() {New Pet With {.Name = "Belle", .Age = 8}}}, _
          New Person With {.LastName = "Philips", _
                           .Pets = New Pet() {New Pet With {.Name = "Sweetie", .Age = 2}, _
                                              New Pet With {.Name = "Rover", .Age = 13}}}})

    ' Determine which people have pets that are all older than 5.
    Dim names = From person In people _
                Where person.Pets.AsQueryable().All(Function(pet) pet.Age > 5) _
                Select person.LastName

    For Each name As String In names
        Console.WriteLine(name)
    Next

    ' This code produces the following output:
    '
    ' Haas
    ' Antebi

End Sub

Poznámky

Tato metoda má alespoň jeden parametr typu Expression<TDelegate> , jehož argument typu je jedním z Func<T,TResult> typů. Pro tyto parametry můžete předat výraz lambda, který se zkompiluje do Expression<TDelegate>.

Metoda All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) vygeneruje metodu MethodCallExpression , která představuje volání All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) sebe sama jako konstruovanou obecnou metodu. Pak předá MethodCallExpression metodu IQueryProviderExecute<TResult>(Expression) reprezentované Provider vlastností parametru source .

Chování dotazu, ke kterému dochází v důsledku spuštění stromu výrazů, který představuje volání All<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) , závisí na implementaci typu parametru source . Očekávané chování je, že určuje, jestli všechny prvky v source splňují podmínku v predicate.

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