Question

在WinForms中，对于所有控件，都有.OnDisposed覆盖，Disposed事件和IsDisposed属性。

WPF似乎没有等价物。

如何在WPF应用程序中监听UserControl的处理？

更清楚;我需要知道何时删除控件。原因是对于某些控件我想保持对控件的静态引用以便于访问它，并且当控件不再在范围内时，我需要将该引用设置为null。

更清楚：

public class Foo : UserControl{
    private static Foo _Instance;
    //For ease of access. I do not want to have to call Control.Control.Control.Control.FooVar.DoSomething() when I can call Foo.Instance.DoSomething()
    public static Foo Instance { get { return Foo._Instance ?? new Foo() } }

    public Foo(){
        this.InitializeComponents();
        /*Other Initialization Stuff*/
        Foo._Instance = this; /*<---- This needs to be set to null when Foo is closed/disposed/removed/out of scope etc.*/
    }        
}

Answer 1

如果你想静态引用对象，但没有将它们保存在内存中，你可以随时选择WeakReference<T>

$doc = new DOMDocument();//DOMDocument()
if(file_exists("urls.xml"))
$doc->load("article.xml");
$racine=$doc->documentElement;
$racine1=$doc->createElement("URL");//create element URL
$link=$doc->createElement("link"); //reate element link
$racine1->appendChild($link);   //add element link to element URL
$textlink=$doc->createTextNode("text");// create textnode with value "text"
$link->appendChild($textlink); // add textnode to element link
$racine->appendChild($racine1); // add element URl to Racine URLS
$doc->appendChild($racine);
$xml=$doc->saveXML();
$doc->save("urls.xml");
header("content-type: text/xml");

然而，这引入了这样的可能性：根据GC的想法，您可以在快速关闭和刷新页面后获得相同的控件。在这种情况下，您应确保public partial class MyControl : UserControl { private readonly static WeakReference<MyControl> _instance = new WeakReference<T>(null); public static MyControl Instance { get { UserControl result; if(!_instance.TryGetTarget(out result)) _instance.SetTarget(result = new MyControl()); return result; } } }事件触发实例无效

Unloaded

然后在你的XAML ......

// Ensure the instance is cleared when unloading
public void OnUnloaded(object sender, RoutedEventArgs args)
{
    _instance.SetTarget(null);
}

WPF控制处置

1 个答案: