Articolo
11/18/2011

Enumerable.Any<TSource> Method (IEnumerable<TSource>)

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Determines whether a sequence contains any elements.

Namespace: System.Linq
Assembly: System.Core (in System.Core.dll)

Syntax

'Declaration
<ExtensionAttribute> _
Public Shared Function Any(Of TSource) ( _
    source As IEnumerable(Of TSource) _
) As Boolean

public static bool Any<TSource>(
    this IEnumerable<TSource> source
)

Type Parameters

TSource
The type of the elements of source.

Parameters

source
Type: System.Collections.Generic.IEnumerable<TSource>
The IEnumerable<T> to check for emptiness.

Return Value

Type: System.Boolean
true if the source sequence contains any elements; otherwise, false.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IEnumerable<TSource>. When you use instance method syntax to call this method, omit the first parameter.

Exceptions

Exception	Condition
ArgumentNullException	source is nulla null reference (Nothing in Visual Basic).

Remarks

Note:
This method does not return any one element of a collection. Instead, it determines whether the collection contains any elements.

The enumeration of source is stopped as soon as the result can be determined.

In Visual Basic query expression syntax, an Aggregate Into Any() clause translates to an invocation of Any.

Examples

The following code example demonstrates how to use Any to determine whether a sequence contains any elements.

      ' Create a list of Integers.
      Dim numbers As New List(Of Integer)(New Integer() {1, 2})

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

      ' Display the output.
      Dim text As String = IIf(hasElements, "not ", "")
      outputBlock.Text += "The list is " & text & "empty." & vbCrLf

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

         List<int> numbers = new List<int> { 1, 2 };
         bool hasElements = numbers.Any();

         outputBlock.Text += String.Format("The list {0} empty.",
             hasElements ? "is not" : "is") + "\n";

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

The Boolean value that the Any<TSource>(IEnumerable<TSource>) method returns is typically used in the predicate of a where clause (Where clause in Visual Basic) or a direct call to the Where<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>) method. The following example demonstrates this use of the Any method.

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.Any() _
               Select person.LastName

   For Each name As String In names
      outputBlock.Text &= name & vbCrLf
   Next

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

End Sub

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.Any()
                               select person.LastName;

   foreach (string name in names)
   {
      outputBlock.Text += name + "\n";
   }

   /* This code produces the following output:

      Haas
      Fakhouri
      Philips
   */
}

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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