Queryable.Any 方法

定義

命名空間:

System.Linq

組件:

System.Linq.Queryable.dll

判斷 IQueryable<T> 序列的任何項目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項目。
Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>)	判斷序列的任何項目是否符合條件。

Any<TSource>(IQueryable<TSource>)

來源:

Queryable.cs

判斷序列是否包含任何項目。

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 項目的類型。

參數

source

IQueryable<TSource>

要檢查是否為空白的序列。

傳回

Boolean

如果來源序列包含任何項目，則為 true，否則為 false。

例外狀況

ArgumentNullException

source 為 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.

方法傳回的Any<TSource>(IQueryable<TSource>)布爾值通常用於 Visual Basic) 或直接呼叫 Where<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 方法的子句 (Where 子句述where詞中。 下列範例示範此方法的使用 Any 方式。

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

方法 Any<TSource>(IQueryable<TSource>) 會產生 ， MethodCallExpression 表示 Any<TSource>(IQueryable<TSource>) 呼叫本身做為建構的泛型方法。 然後，它會將 傳遞MethodCallExpression至 Execute<TResult>(Expression) 參數的 屬性所Provider表示的 source 方法IQueryProvider。

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

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

來源:

Queryable.cs

判斷序列的任何項目是否符合條件。

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 項目的類型。

參數

source

IQueryable<TSource>

要測試其項目是否符合條件的序列。

predicate

Expression<Func<TSource,Boolean>>

用來測試每個項目是否符合條件的函式。

傳回

Boolean

如果來源序列中的任何項目通過以指定之述詞進行的測試，則為 true，否則為 false。

例外狀況

ArgumentNullException

source 或 predicate 為 null。

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 Expression<TDelegate> 參數，其類型自變數為其中一個 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 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 會產生 ， MethodCallExpression 表示 Any<TSource>(IQueryable<TSource>, Expression<Func<TSource,Boolean>>) 呼叫本身做為建構的泛型方法。 然後，它會將 傳遞MethodCallExpression至 Execute<TResult>(Expression) 參數的 屬性所Provider表示的 source 方法IQueryProvider。

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