WeakReference.Target 属性

定义

命名空间:

System

程序集:

System.Runtime.dll

Source:

WeakReference.cs

获取或设置当前 WeakReference 对象引用的对象（目标）。

public:
 virtual property System::Object ^ Target { System::Object ^ get(); void set(System::Object ^ value); };

public virtual object? Target { get; set; }

member this.Target : obj with get, set

Public Overridable Property Target As Object

属性值

Object

如果当前 WeakReference 对象引用的对象已被垃圾回收，则为 null；否则引用当前 WeakReference 对象所引用的对象。

例外

InvalidOperationException

对目标对象的引用无效。 设置此属性时，如果值为 null 引用或在设置操作期间终止了该对象，则可能引发此异常。

示例

以下示例尝试从具有弱引用的 对象的缓存中获取 对象。 如果对象已回收进行垃圾回收，则会生成一个新的 对象。 此示例是为 类提供的更大示例的一 WeakReference 部分。

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;

match _cache[index].Target with
| :? Data as d->
    // Object was obtained with the weak reference.
    printfn $"Regenerate object at {index}: No"
    d
| _ ->
    // If the object was reclaimed, generate a new one.
    printfn $"Regenerate object at {index}: Yes"
    let d = Data index
    _cache[index].Target <- d
    regenCount <- regenCount + 1
    d

 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

注解

将此属性设置为目标对象后，请确保没有对对象的其他强引用;否则，将不会收集它。

另请参阅

• Object
• GC
• 弱引用