如何在WPF ItemsControl中重写预定义的依赖项Properties ItemsSource的PropertyChangedCallback [英] How to Override PropertyChangedCallback of a predefined Dependency Property ItemsSource in a WPF ItemsControl

问题描述

如何覆盖 PropertyChangedCallback 预定义的依赖项属性 ItemsSource 在WPF ItemsControl 中。

我开发了继承的WPF自定义控件来自 ItemsControl 。在此，我使用了预定义的依赖项属性 ItemsSource 。这样，一旦 Collection 得到更新，我就需要监视和检查数据。

I developed a WPF Custom Control inherited from ItemsControl. In that I used the predefined Dependency Property ItemsSource. In that I need to monitor and check data once the Collection gets updated.

我在Google中搜索了很多内容，但是找不到任何相关的解决方案来满足我的要求。

I searched a lot in google, but I can't able to find any related solution to fulfill my requirement.

https://msdn.microsoft.com/zh-CN/library/ system.windows.controls.itemscontrol.itemssource（v = vs.110）.aspx

请协助我，要覆盖的方法名称是什么？ ...

推荐答案

在中调用 OverrideMetadata 派生的ItemsSource类的静态构造函数：

Call OverrideMetadata in a static constructor of your derived ItemsSource class:

public class MyItemsControl : ItemsControl
{
    static MyItemsControl()
    {
        ItemsSourceProperty.OverrideMetadata(
            typeof(MyItemsControl),
            new FrameworkPropertyMetadata(OnItemsSourcePropertyChanged));
    }

    private static void OnItemsSourcePropertyChanged(
        DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        ((MyItemsControl)obj).OnItemsSourcePropertyChanged(e);
    }

    private void OnItemsSourcePropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        var oldCollectionChanged = e.OldValue as INotifyCollectionChanged;
        var newCollectionChanged = e.NewValue as INotifyCollectionChanged;

        if (oldCollectionChanged != null)
        {
            oldCollectionChanged.CollectionChanged -= OnItemsSourceCollectionChanged;
        }

        if (newCollectionChanged != null)
        {
            newCollectionChanged.CollectionChanged += OnItemsSourceCollectionChanged;
            // in addition to adding a CollectionChanged handler
            // any already existing collection elements should be processed here
        }
    }

    private void OnItemsSourceCollectionChanged(
        object sender, NotifyCollectionChangedEventArgs e)
    {
        // handle collection changes here
    }
}

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