WeakReference.Target 屬性

定義

命名空間:
System
組件:
mscorlib.dll, System.Runtime.dll
組件:
netstandard.dll, System.Runtime.dll
組件:
System.Runtime.dll
組件:
mscorlib.dll
組件:
netstandard.dll
來源:
WeakReference.cs
來源:
WeakReference.cs
來源:
WeakReference.cs
來源:
WeakReference.cs
來源:
WeakReference.cs

取得或設定目前 WeakReference 物件所參考的物件（目標）。

public:
 virtual property System::Object ^ Target { System::Object ^ get(); void set(System::Object ^ value); };
public virtual object Target { get; set; }
public virtual object? Target { get; set; }
member this.Target : obj with get, set
Public Overridable Property Target As Object

屬性值

Object

null 如果目前物件所參考 WeakReference 的物件已被垃圾回收;否則，則是對當前 WeakReference 物件所參考物件的參考。

例外狀況

InvalidOperationException

對目標物件的引用無效。 若值為空參考或物件在設定操作中已被最終確定，則可拋出此例外。

範例

以下範例嘗試從一個具有弱參考的物件快取中取得一個物件。 若物件被回收進行垃圾回收，則會產生一個新的物件。 此範例是本類別更大 WeakReference 範例的一部分。

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

備註

將此屬性設定為目標物件後，確保沒有其他強參考物件;否則，該稅款將不被收取。

適用於

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