WeakReference WeakReference WeakReference WeakReference Class

Definición

Representa una referencia débil, que hace referencia a un objeto mientras sigue permitiendo que la recolección de elementos no utilizados lo reclame.Represents a weak reference, which references an object while still allowing that object to be reclaimed by garbage collection.

public ref class WeakReference : System::Runtime::Serialization::ISerializable
[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public class WeakReference : System.Runtime.Serialization.ISerializable
type WeakReference = class
    interface ISerializable
Public Class WeakReference
Implements ISerializable
Herencia
WeakReferenceWeakReferenceWeakReferenceWeakReference
Atributos
Implementaciones

Ejemplos

El ejemplo siguiente muestra cómo puede usar referencias débiles para mantener una caché de objetos como un recurso para una aplicación.The following example demonstrates how you can use weak references to maintain a cache of objects as a resource for an application. La memoria caché se construye utilizando un IDictionary<TKey,TValue> de WeakReference objetos ordenados por un valor de índice.The cache is constructed using an IDictionary<TKey,TValue> of WeakReference objects keyed by an index value. El Target propiedad para el WeakReference objetos es un objeto en una matriz de bytes que representa los datos.The Target property for the WeakReference objects is an object in a byte array that represents data.

El ejemplo aleatoriamente tiene acceso a objetos en la memoria caché.The example randomly accesses objects in the cache. Si un objeto se reclama la recolección, se vuelve a generar un nuevo objeto de datos; en caso contrario, el objeto está disponible para acceso debido a la referencia débil.If an object is reclaimed for garbage collection, a new data object is regenerated; otherwise, the object is available to access because of the weak reference.

using System;
using System.Collections.Generic;

public class Program
{
    public static void Main()
    {
        // Create the cache.
        int cacheSize = 50;
        Random r = new Random();
        Cache c = new Cache(cacheSize);

        string DataName = "";
        GC.Collect(0);
        
        // Randomly access objects in the cache.
        for (int i = 0; i < c.Count; i++) {
            int index = r.Next(c.Count);

            // Access the object by getting a property value.
            DataName = c[index].Name;
        }
        // Show results.
        double regenPercent = c.RegenerationCount/(double)c.Count;
        Console.WriteLine("Cache size: {0}, Regenerated: {1:P2}%", c.Count, regenPercent);
    }
}

public class Cache
{
    // Dictionary to contain the cache.
    static Dictionary<int, WeakReference> _cache;

    // Track the number of times an object is regenerated.
    int regenCount = 0;   

    public Cache(int count)
    {
        _cache = new Dictionary<int, WeakReference>();

        // Add objects with a short weak reference to the cache.
       for (int i = 0; i < count; i++) {
            _cache.Add(i, new WeakReference(new Data(i), false));
        }
    }

    // Number of items in the cache.
    public int Count
    {
        get {  return _cache.Count; }
    }

    // Number of times an object needs to be regenerated.
    public int RegenerationCount
    {
        get { return regenCount; }
    }

    // Retrieve a data object from the cache.
    public Data this[int index]
    {
        get {
            Data d = _cache[index].Target as Data;
            if (d == null) {
                // If the object was reclaimed, generate a new one.
                Console.WriteLine("Regenerate object at {0}: Yes", index);
                d = new Data(index);
                _cache[index].Target = d;
                regenCount++;
            }
            else {
                // Object was obtained with the weak reference.
                Console.WriteLine("Regenerate object at {0}: No", index);
            }

            return d;
       }
    }
}

// This class creates byte arrays to simulate data.
public class Data
{
    private byte[] _data;
    private string _name;

    public Data(int size)
    {
        _data = new byte[size * 1024];
        _name = size.ToString();
    }

    // Simple property.
    public string Name
    {
        get { return _name; }
    }
}
// Example of the last lines of the output:
//
// ...
// Regenerate object at 36: Yes
// Regenerate object at 8: Yes
// Regenerate object at 21: Yes
// Regenerate object at 4: Yes
// Regenerate object at 38: No
// Regenerate object at 7: Yes
// Regenerate object at 2: Yes
// Regenerate object at 43: Yes
// Regenerate object at 38: No
// Cache size: 50, Regenerated: 94%
Imports System.Collections.Generic

Public Class Example
    Public Shared Sub Main()
        ' Create the cache. 
        Dim cacheSize As Integer = 50
        Dim r As Random = New Random()
        Dim c As Cache = New Cache(cacheSize)

        Dim DataName As String = "" 
        GC.Collect(0)
        
        ' Randomly access objects in the cache. 
        For ctr As Integer = 0 To C.Count - 1 
            Dim index As Integer = r.Next(c.Count)

            ' Access the object by getting a property value.
            DataName = c(index).Name
        Next 

        ' Show results. 
        Dim regenPercent As Double = c.RegenerationCount * 100 / c.Count
        Console.WriteLine("Cache size: {0}, Regenerated: {1}%", c.Count, regenPercent)
    End Sub 
End Class 

Public Class Cache
    ' Dictionary to contain the cache. 
    Private Shared _cache As Dictionary(Of Integer, WeakReference)

    ' Track the number of times an object is regenerated. 
    Dim regenCount As Integer = 0

    Public Sub New(ByVal count As Integer)
        _cache = New Dictionary(Of Integer, WeakReference)

        ' Add data objects with a short weak reference to the cache. 
        For ctr = 0 To count - 1
            _cache.Add(ctr, New WeakReference(New Data(ctr)))
        Next
    End Sub 

    ' Number of items in the cache. 
    Public ReadOnly Property Count() As Integer 
        Get 
            Return _cache.Count
        End Get 
    End Property 

    ' Number of times an object needs to be regenerated. 
    Public ReadOnly Property RegenerationCount() As Integer 
        Get 
            Return regenCount
        End Get 
    End Property 

    ' Retrieve a data object from the cache. 
    Default Public ReadOnly Property Item(ByVal index As Integer) As Data
        Get 
            Dim d As Data = TryCast(_cache(index).Target, Data)
            ' If the object was reclaimed, generate a new one.
            If d Is Nothing Then 
                Console.WriteLine("Regenerate object at {0}: Yes", index)
                d = New Data(index)
                _cache(index).Target = d
                regenCount += 1
           Else 
                ' Object was obtained with the weak reference.
                Console.WriteLine("Regenerate object at {0}: No", index.ToString())
            End If 
            Return d
        End Get 
    End Property 
End Class 

' Class that creates byte arrays to simulate data. 
Public Class Data
    Private _data() As Byte 
    Private _name As String 

    Public Sub New(ByVal size As Integer)
        _data = New Byte(((size * 1024)) - 1) {}
        _name = size.ToString
    End Sub 

    ' Simple property for accessing the object. 
    Public ReadOnly Property Name() As String 
        Get 
            Return _name
        End Get 
    End Property 
End Class 
' Example of the last lines of the output: 
' ... 
' Regenerate object at 36: Yes 
' Regenerate object at 8: Yes 
' Regenerate object at 21: Yes 
' Regenerate object at 4: Yes 
' Regenerate object at 38: No 
' Regenerate object at 7: Yes 
' Regenerate object at 2: Yes 
' Regenerate object at 43: Yes 
' Regenerate object at 38: No 
' Cache size: 50, Regenerated: 94% 

Comentarios

Una referencia débil permite al recolector de elementos no utilizados recoger un objeto mientras sigue permitiendo que una aplicación para tener acceso al objeto.A weak reference allows the garbage collector to collect an object while still allowing an application to access the object. Si necesita el objeto, puede obtener una referencia fuerte a él y evitar que se están recopilando.If you need the object, you can still obtain a strong reference to it and prevent it from being collected. Para obtener más información acerca de cómo usar breve y referencias débiles largas, consulte referencias débiles.For more information about how to use short and long weak references, see Weak References.

Constructores

WeakReference() WeakReference() WeakReference() WeakReference()
WeakReference(Object) WeakReference(Object) WeakReference(Object) WeakReference(Object)

Inicializa una nueva instancia de la clase WeakReference que hace referencia al objeto especificado.Initializes a new instance of the WeakReference class, referencing the specified object.

WeakReference(Object, Boolean) WeakReference(Object, Boolean) WeakReference(Object, Boolean) WeakReference(Object, Boolean)

Inicializa una nueva instancia de la clase WeakReference que hace referencia al objeto especificado y utiliza el seguimiento especificado del restablecimiento.Initializes a new instance of the WeakReference class, referencing the specified object and using the specified resurrection tracking.

WeakReference(SerializationInfo, StreamingContext) WeakReference(SerializationInfo, StreamingContext) WeakReference(SerializationInfo, StreamingContext) WeakReference(SerializationInfo, StreamingContext)

Inicializa una nueva instancia de la clase WeakReference utilizando datos sin serializar de la serialización y objetos de secuencia especificados.Initializes a new instance of the WeakReference class, using deserialized data from the specified serialization and stream objects.

Propiedades

IsAlive IsAlive IsAlive IsAlive

Obtiene un valor que indica si el objeto al que hace referencia el objeto WeakReference actual ha sido detectado durante la recolección de elementos no utilizados.Gets an indication whether the object referenced by the current WeakReference object has been garbage collected.

Target Target Target Target

Obtiene o establece el objeto (destino) al que hace referencia el objeto WeakReference actual.Gets or sets the object (the target) referenced by the current WeakReference object.

TrackResurrection TrackResurrection TrackResurrection TrackResurrection

Obtiene un valor que indica si se debe realizar un seguimiento del objeto al que hace referencia el objeto WeakReference actual después de su finalización.Gets an indication whether the object referenced by the current WeakReference object is tracked after it is finalized.

Métodos

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina si el objeto especificado es igual al objeto actual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
Finalize() Finalize() Finalize() Finalize()

Descarta la referencia al destino representado por el objeto WeakReference actual.Discards the reference to the target represented by the current WeakReference object.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Sirve como la función hash predeterminada.Serves as the default hash function.

(Inherited from Object)
GetObjectData(SerializationInfo, StreamingContext) GetObjectData(SerializationInfo, StreamingContext) GetObjectData(SerializationInfo, StreamingContext) GetObjectData(SerializationInfo, StreamingContext)

Rellena un objeto SerializationInfo con todos los datos necesarios para serializar el objeto WeakReference actual.Populates a SerializationInfo object with all the data needed to serialize the current WeakReference object.

GetType() GetType() GetType() GetType()

Obtiene el Type de la instancia actual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Crea una copia superficial del objeto Object actual.Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

Devuelve una cadena que representa el objeto actual.Returns a string that represents the current object.

(Inherited from Object)

Seguridad

SecurityPermission
Para poder llamar a código no administrado.for the ability to call unmanaged code. Valor de petición: InheritanceDemand; Valor de permiso: UnmanagedCodeDemand value: InheritanceDemand; Permission value: UnmanagedCode

Se aplica a

Consulte también: