Question

我正准备一个具有多个对象的应用程序，每个对象都有一个整数id和字符串数据。我希望具有相同id的对象的数据相同。我将调用此对象SharedObject（此对象的行为类似于某些数据库表的ViewModel。）

有人可能会说这很容易。您可以创建单个对象，并在每次需要时引用它。但实际上这种方式对我来说不起作用，因为我无法预测对象的创建时间和地点。

因此，为了解决这个问题，我决定在SharedObject类中放置一个静态事件，并在任何SharedObject数据发生更改时调用它（比如INotifyPropertyChanged中的PropertyChanged事件，但我的是静态的。这将使它对SharedObject的每个实例都可见），但问题是我最终得到了一个充满内存泄漏的程序!!

昨晚我整理出我必须使用弱事件模式来解决内存泄漏问题。

我在昨晚搜索了网络，以便完全实现弱事件模式，但我最终没有删除或删除页面。

最后，我想出了如何用弱事件模式来做到这一点我创建了一个测试项目来测试这种方法，但它没有用，无法调用ReceiveWeakEvent事件。

我错过了什么吗？或者实现这种模式的正确方法是什么？

顺便说一句，我使用.net 4，因为我需要我的应用程序来支持Win XP（这是我的客户需要的，不要问我这个问题），所以我不能使用通用的WeakEventManager类。

很抱歉很长的帖子，但是这个问题让我脱掉了头发，并提前感谢。

以下是完整的应用程序代码：

SharedObject类：

public class SharedObject :INotifyPropertyChanged,IWeakEventListener
{
    static WaekEvent sheardEvent = new WaekEvent();

    public event PropertyChangedEventHandler PropertyChanged;

    public int ID { get; private set; }

    public SharedObject(int id)
    {
        this.ID = id;
        SharedWeakEventManager.AddListener(sheardEvent, this);
    }

    string data;
    public string Data
    {
        get
        {
            return data;
        }
        set
        {
            if(value != data)
            {
                data = value;
                OnPropertyChanged("Data");
                sheardEvent.RiseSharedEvent(this, new PropertyChangedEventArgs("Data"));
            }
        }
    }

    protected virtual void OnPropertyChanged(string propName)
    {
        PropertyChangedEventHandler handler;
        lock (this)
        {
            handler = PropertyChanged;
        }
        if (handler != null)
            handler.Invoke(this, new PropertyChangedEventArgs(propName));
    }

    void OnSharedPropertyChaingo(object sender,PropertyChangedEventArgs e)
    {
        SharedObject s = sender as SharedObject;
        if (s == null || s.ID != ID)
            return;
        data = s.Data;
        OnPropertyChanged("Data");
    }


    public bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
    {
        if(managerType == typeof(SharedWeakEventManager) && sender is SharedObject)
        {
            OnSharedPropertyChaingo(sender, e as PropertyChangedEventArgs);
        }
        return false;
    }
}

WaekEvent和SharedWeakEventManager类：

public class SharedObject 
{
    public event EventHandler SharedEvent;

    public void RiseSharedEvent(object sender, EventArgs args)
    {
        if (SharedEvent != null)
            SharedEvent.Invoke(sender, args);
    }
}
public class SharedWeakEventManager : WeakEventManager
{
    public static SharedWeakEventManager CurrentManager
    {
        get
        {
            var manager_type = typeof(SharedWeakEventManager);
            var manager = WeakEventManager.GetCurrentManager(manager_type) as SharedWeakEventManager;

            if (manager == null)
            {
                manager = new SharedWeakEventManager();
                WeakEventManager.SetCurrentManager(manager_type, manager);
            }

            return manager;
        }
    }

    public static void AddListener(WaekEvent source, IWeakEventListener listener)
    {
        CurrentManager.ProtectedAddListener(source, listener);
    }

    public static void RemoveListener(WaekEvent source, IWeakEventListener listener)
    {
        CurrentManager.ProtectedRemoveListener(source, listener);
    }

    protected override void StartListening(object source)
    {
        ((WaekEvent)source).SharedEvent += this.DeliverEvent;
    }

    protected override void StopListening(object source)
    {
        ((WaekEvent)source).SharedEvent -= this.DeliverEvent;
    }
}

MainWindow的XAML部分：

<Window x:Class="WpfApplication1.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <ListView x:Name="View" Margin="10,49,10,10" SelectionChanged="ListView_SelectionChanged">
        <ListView.View>
            <GridView>
                <GridViewColumn Header="ID" Width="100" DisplayMemberBinding="{Binding ID}"/>
                <GridViewColumn Header="Data" Width="100" DisplayMemberBinding="{Binding Data}"/>
            </GridView>
        </ListView.View>
    </ListView>
    <Button Content="New" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="10,13.01,0,0" Click="Button_Click"/>
    <TextBox x:Name="IDText" HorizontalAlignment="Left" Height="23" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="92" Margin="136.2,11,0,0"/>
    <TextBox x:Name="DataText" HorizontalAlignment="Left" Height="23" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="92" Margin="280.799,11,0,0" TextChanged="DataText_TextChanged"/>
    <TextBlock HorizontalAlignment="Left" TextWrapping="Wrap" Text="ID" VerticalAlignment="Top" Margin="119.593,14,0,0"/>
    <TextBlock HorizontalAlignment="Left" TextWrapping="Wrap" Text="Data" VerticalAlignment="Top" Margin="251.106,15.01,0,0"/>
    <Button Content="Remove" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="377.799,12,0,0" Click="Button_Click_1"/>

</Grid>

MainWindow类：

public partial class MainWindow : Window
{
    private ObservableCollection<SharedObject> sharedObjects;
    public ObservableCollection<SharedObject> SharedObjects
    {
        get
        {
            if (sharedObjects == null)
                sharedObjects = new ObservableCollection<SharedObject>();
            return sharedObjects;
        }
    }

    public SharedObject SelelectedObject { get; set; }
    public MainWindow()
    {
        InitializeComponent();
        View.ItemsSource = SharedObjects;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        int id;
        if (!int.TryParse(IDText.Text, out id))
            return;

        SharedObject x = new SharedObject(id);
        x.Data = DataText.Text;
        SharedObjects.Add(x);
    }

    private void Button_Click_1(object sender, RoutedEventArgs e)
    {
        if (SelelectedObject == null)
            return;
        SharedObjects.Remove(SelelectedObject);
        SelelectedObject = null;
    }

    private void DataText_TextChanged(object sender, TextChangedEventArgs e)
    {
        if (SelelectedObject != null)
            SelelectedObject.Data = DataText.Text;
    }

    private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        SelelectedObject = View.SelectedItem as SharedObject;
        if (SelelectedObject == null)
            return;
        IDText.Text = SelelectedObject.ID.ToString();
        DataText.Text = SelelectedObject.Data;
    }
}

为共享属性MVVM

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