NETFramework上的DataTemplate(XAML)中的WPF事件取消訂閱泄漏

想象一下 aUserControl在 aListBox中有CheckBoxa DataTemplate。在ItemsSource對ListBox一些全域串列。在CheckBox具有Checked/Unchecked連接到它的活動。

<ListBox ItemsSource="{Binding Source={x:Static a:MainWindow.Source}}">
    <ListBox.ItemTemplate>
        <DataTemplate DataType="{x:Type a:Data}">
            <CheckBox Content="{Binding Path=Name}"
                      Checked="ToggleButton_OnChecked"
                      Unchecked="ToggleButton_OnUnchecked"
                      IsChecked="{Binding Path=IsEnabled}"
                      Padding="10"
                      VerticalContentAlignment="Center"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

我正在主視窗的日志中記錄加載/卸載/檢查/未檢查事件。

    private void ToggleButton_OnChecked(object sender, RoutedEventArgs e)
    {
        Log("Checked");
    }

    private void ToggleButton_OnUnchecked(object sender, RoutedEventArgs e)
    {
        Log("Unchecked");
    }

    private void UserControl1_OnLoaded(object sender, RoutedEventArgs e)
    {
        Log("Loaded");
    }

    private void UserControl1_OnUnloaded(object sender, RoutedEventArgs e)
    {
        Log("Unloaded");
    }

主視窗具有UserControl1實體的動態串列（僅從一個開始）。有添加/洗掉按鈕允許我添加更多實體。

<UniformGrid Rows="2">
    <DockPanel>
        <Button DockPanel.Dock="Top" Click="Add">Add</Button>
        <Button DockPanel.Dock="Top" Click="Remove">Remove</Button>
        <ListBox x:Name="ListBox">
            <local:UserControl1 />
        </ListBox>
    </DockPanel>

    <ListBox ItemsSource="{Binding ElementName=This,Path=Log}" FontFamily="Courier New"/>
</UniformGrid>

視窗的代碼隱藏：

    private void Add(object sender, RoutedEventArgs e)
    {
        ListBox.Items.Add(new UserControl1());
    }

    private void Remove(object sender, RoutedEventArgs e)
    {
        if (ListBox.Items.Count == 0) return;
        ListBox.Items.RemoveAt(0);
    }

When I run the app there is just one UserControl1 instance. If I add one more and then immediately remove one of them, then click the one and only checkbox on the screen, I see two "Checked" events logged. If I now uncheck it, there are two "Unchecked" events (even though "Unloaded" event was previously clearly logged. The hex numbers on the left show the output of a GetHashCode() which clearly shows the events were handled by distinct UserControl1 instances.

So even though one of UserControl1 gets unloaded, the events don't seem to get unsubscribed automatically. I have tried upgrading to NET Framework 4.8 to no avail. I see the same behavior. If I add 10 new controls and remove them immediately, I will observe 10 "Checked" or "Unchecked" events.

我曾嘗試搜索類似的問題，但找不到。是我遺漏了什么還是我剛剛遇到了一個錯誤？尋找解決方法。

GitHub 上提供了完整的源代碼。https://github.com/wpfwannabe/datacontext-event-leak

uj5u.com熱心網友回復：

在MVVM模式中，視圖被系結到視圖模型并且在垃圾收集完成它的作業時不會存活。

在您提供的示例中，視圖模型是一個靜態物件，根據定義不能被垃圾收集，因此視圖也不能被垃圾收集。

沒有自動解除系結，因為你可以重復使用的用戶控制元件的實體（也可以是Loaded和UnLoaded多次）。

修復此記憶體泄漏的最簡單1方法是在unload上進行解除系結：

濕巾

// First give the ListBox a name
<ListBox x:Name="ListBox" ItemsSource="{Binding Source={x:Static a:MainWindow.Source}}">

背后的代碼

private void UserControl1_OnUnloaded(object sender, RoutedEventArgs e)
{
    Log("Unloaded");
    ListBox.ItemsSource = null;
}

1：正確的方法是將靜態串列包裝在專用的串列視圖模型中，使視圖模型可丟棄（在處置時從靜態串列中解除包裝器的系結），在移除時處置視圖模型。

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