WeakReference 클래스

정의

가비지 수집에 의한 개체 회수를 허용하면서 개체를 참조하는 약한 참조를 나타냅니다.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
상속
WeakReference
특성
구현

예제

다음 예제에서는 약한 참조를 사용 하 여 애플리케이션에 대 한 리소스로 개체의 캐시를 유지 하는 방법을 보여 줍니다.The following example demonstrates how you can use weak references to maintain a cache of objects as a resource for an application. 캐시를 사용 하 여 생성 되는 IDictionary<TKey,TValue>WeakReference 인덱스 값에서 키 지정 된 개체입니다.The cache is constructed using an IDictionary<TKey,TValue> of WeakReference objects keyed by an index value. Target 에 대 한 속성을 WeakReference 개체는 데이터를 나타내는 바이트 배열에서 개체입니다.The Target property for the WeakReference objects is an object in a byte array that represents data.

이 예제에서는 캐시의 개체를 임의로 액세스합니다.The example randomly accesses objects in the cache. 가비지 컬렉션에 대 한 개체 회수를 새 데이터 개체를 다시 생성 됩니다. 그렇지 않으면 개체는 약한 참조에 액세스할 수 있습니다.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% 

설명

약한 참조는 가비지 수집기가 개체에 액세스 하려면 애플리케이션 허용 하면서 개체를 수집할 수 있습니다.A weak reference allows the garbage collector to collect an object while still allowing an application to access the object. 개체를 해야 하는 경우 여전히에 대 한 강한 참조를 수집 되지 않도록 방지 합니다.If you need the object, you can still obtain a strong reference to it and prevent it from being collected. 사용 하 여 short 및 long weak 방법에 대 한 자세한 내용은 참조 하세요. 약한 참조합니다.For more information about how to use short and long weak references, see Weak References.

생성자

WeakReference()
WeakReference(Object)

지정된 개체를 참조하여 WeakReference 클래스의 새 인스턴스를 초기화합니다.Initializes a new instance of the WeakReference class, referencing the specified object.

WeakReference(Object, Boolean)

지정된 개체를 참조하고 지정된 재활성화 추적을 사용하여 WeakReference 클래스의 새 인스턴스를 초기화합니다.Initializes a new instance of the WeakReference class, referencing the specified object and using the specified resurrection tracking.

WeakReference(SerializationInfo, StreamingContext)

지정된 serialization 및 스트림 개체의 deserialize된 데이터를 사용하여 WeakReference 클래스의 새 인스턴스를 초기화합니다.Initializes a new instance of the WeakReference class, using deserialized data from the specified serialization and stream objects.

속성

IsAlive

현재 WeakReference 개체에서 참조하는 개체가 가비지 수집되었는지 여부를 가져옵니다.Gets an indication whether the object referenced by the current WeakReference object has been garbage collected.

Target

현재 WeakReference 개체에서 참조하는 개체(대상)를 가져오거나 설정합니다.Gets or sets the object (the target) referenced by the current WeakReference object.

TrackResurrection

현재 WeakReference 개체에서 참조되는 개체가 종료된 후 추적되는지 여부를 가져옵니다.Gets an indication whether the object referenced by the current WeakReference object is tracked after it is finalized.

메서드

Equals(Object)

지정한 개체와 현재 개체가 같은지 여부를 확인합니다.Determines whether the specified object is equal to the current object.

(다음에서 상속됨 Object)
Finalize()

현재 WeakReference 개체가 나타내는 대상에 대한 참조를 삭제합니다.Discards the reference to the target represented by the current WeakReference object.

GetHashCode()

기본 해시 함수로 작동합니다.Serves as the default hash function.

(다음에서 상속됨 Object)
GetObjectData(SerializationInfo, StreamingContext)

현재 SerializationInfo 개체를 serialize하는 데 필요한 모든 데이터로 WeakReference 개체를 채웁니다.Populates a SerializationInfo object with all the data needed to serialize the current WeakReference object.

GetType()

현재 인스턴스의 Type을 가져옵니다.Gets the Type of the current instance.

(다음에서 상속됨 Object)
MemberwiseClone()

현재 Object의 단순 복사본을 만듭니다.Creates a shallow copy of the current Object.

(다음에서 상속됨 Object)
ToString()

현재 개체를 나타내는 문자열을 반환합니다.Returns a string that represents the current object.

(다음에서 상속됨 Object)

보안

SecurityPermission
비관리 코드를 호출할 수 있습니다.for the ability to call unmanaged code. 요청 값: InheritanceDemand; 권한 값: UnmanagedCodeDemand value: InheritanceDemand; Permission value: UnmanagedCode

적용 대상

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