Queryable.Any 方法

定義

命名空間:

System.Linq

組件:

System.Linq.Queryable.dll

判斷 IQueryable<T> 序列的任何專案是否存在或符合條件。

多載

Any<TSource>(IQueryable<TSource>)	判斷序列是否包含任何專案。
Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)	判斷序列的任何專案是否符合條件。

Any<TSource>(IQueryable<TSource>)

來源:

Queryable.cs

判斷序列是否包含任何專案。

public:
generic <typename TSource>
[System::Runtime::CompilerServices::Extension]
 static bool Any(System::Linq::IQueryable<TSource> ^ source);

public static bool Any<TSource> (this System.Linq.IQueryable<TSource> source);

static member Any : System.Linq.IQueryable<'Source> -> bool

<Extension()>
Public Function Any(Of TSource) (source As IQueryable(Of TSource)) As Boolean

類型參數

TSource

source專案的型別。

參數

source

IQueryable<TSource>

要檢查是否為空的序列。

傳回

Boolean

如果來源序列包含任何專案，true;否則，false。

例外狀況

ArgumentNullException

source null。

範例

下列程式代碼範例示範如何使用 Any<TSource>(IQueryable<TSource>) 來判斷序列是否包含任何專案。

List<int> numbers = new List<int> { 1, 2 };

// Determine if the list contains any elements.
bool hasElements = numbers.AsQueryable().Any();

Console.WriteLine("The list {0} empty.",
    hasElements ? "is not" : "is");

// This code produces the following output:
//
// The list is not empty.

Dim numbers As New List(Of Integer)(New Integer() {1, 2})

' Determine if the list contains any elements.
Dim hasElements As Boolean = numbers.AsQueryable().Any()

MsgBox(String.Format("The list {0} empty.", _
    IIf(hasElements, "is not", "is")))

' This code produces the following output:
'
' The list is not empty.

Any<TSource>(IQueryable<TSource>) 方法傳回的布爾值通常用於 where 子句的述詞（Visual Basic 中的Where 子句）或直接呼叫 Where<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法。 下列範例示範如何使用 Any 方法。

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 AnyEx2()
{
    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 Person { LastName = "Philips",
                       Pets = new Pet[] { new Pet { Name = "Sweetie", Age = 2},
                                          new Pet { Name = "Rover", Age = 13}} }
        };

    // Determine which people have a non-empty Pet array.
    IEnumerable<string> names = from person in people
                                where person.Pets.AsQueryable().Any()
                                select person.LastName;

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

    /* This code produces the following output:

       Haas
       Fakhouri
       Philips
    */
}

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 AnyEx2()
    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 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 a non-empty Pet array.
    Dim names = From person In people _
                Where person.Pets.AsQueryable().Any() _
                Select person.LastName

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

    ' This code produces the following output:
    '
    ' Haas
    ' Fakhouri
    ' Philips

End Sub

備註

Any<TSource>(IQueryable<TSource>) 方法會產生 MethodCallExpression，代表呼叫 Any<TSource>(IQueryable<TSource>) 本身做為建構的泛型方法。 然後，它會將 MethodCallExpression 傳遞至 source 參數 Provider 屬性所表示之 IQueryProvider 的 Execute<TResult>(Expression) 方法。

執行表示呼叫 Any<TSource>(IQueryable<TSource>) 表達式樹狀結構的查詢行為，取決於 source 參數類型的實作。 預期的行為是它會判斷 source 是否包含任何專案。

Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)

來源:

Queryable.cs

判斷序列的任何專案是否符合條件。

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

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

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

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

類型參數

TSource

source專案的型別。

參數

source

IQueryable<TSource>

序列，其專案要測試條件。

predicate

Expression<Func<TSource,Boolean>>

用來測試條件每個專案的函式。

傳回

Boolean

如果來源序列中的任何專案都通過指定述詞中的測試，true;否則，false。

例外狀況

ArgumentNullException

source 或 predicatenull。

範例

下列程式代碼範例示範如何使用 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 來判斷序列中的任何專案是否符合條件。

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

public static void AnyEx3()
{
    // Create an array of Pet objects.
    Pet[] pets =
        { new Pet { Name="Barley", Age=8, Vaccinated=true },
          new Pet { Name="Boots", Age=4, Vaccinated=false },
          new Pet { Name="Whiskers", Age=1, Vaccinated=false } };

    // Determine whether any pets over age 1 are also unvaccinated.
    bool unvaccinated =
        pets.AsQueryable().Any(p => p.Age > 1 && p.Vaccinated == false);

    Console.WriteLine(
        "There {0} unvaccinated animals over age one.",
        unvaccinated ? "are" : "are not any");
}

// This code produces the following output:
//
//  There are unvaccinated animals over age one.

Structure Pet
    Dim Name As String
    Dim Age As Integer
    Dim Vaccinated As Boolean
End Structure

Shared Sub AnyEx3()
    ' Create an array of Pet objects.
    Dim pets() As Pet = _
        {New Pet With {.Name = "Barley", .Age = 8, .Vaccinated = True}, _
         New Pet With {.Name = "Boots", .Age = 4, .Vaccinated = False}, _
         New Pet With {.Name = "Whiskers", .Age = 1, .Vaccinated = False}}

    ' Determine whether any pets over age 1 are also unvaccinated.
    Dim unvaccinated As Boolean = _
    pets.AsQueryable().Any(Function(p) p.Age > 1 And p.Vaccinated = False)

    MsgBox(String.Format( _
        "There {0} unvaccinated animals over age one.", _
        IIf(unvaccinated, "are", "are not any") _
    ))
End Sub

' This code produces the following output:
'
'  There are unvaccinated animals over age one.

備註

這個方法至少有一個類型參數 Expression<TDelegate> 其類型自變數是其中一個 Func<T,TResult> 類型。 針對這些參數，您可以傳入 Lambda 運算式，並將它編譯為 Expression<TDelegate>。

Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法會產生 MethodCallExpression，代表呼叫 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 本身做為建構的泛型方法。 然後，它會將 MethodCallExpression 傳遞至 source 參數 Provider 屬性所表示之 IQueryProvider 的 Execute<TResult>(Expression) 方法。

執行表示呼叫 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 表達式樹狀結構的查詢行為，取決於 source 參數類型的實作。 預期的行為是，它會判斷 source 的任何專案是否符合 predicate所指定的條件。