Question

I ve got a problem with binding in XAML/WPF. I created Action class which extends FrameworkElement. Each Action has list of ActionItem. The problem is that the Data/DataContext properties of ActionItem are not set, so they are always null.

XAML:

<my:Action DataContext="{Binding}">
    <my:Action.Items>
        <my:ActionItem DataContext="{Binding}" Data="{Binding}" />
    </my:Action.Items>
</my:Action>

C#:

public class Action : FrameworkElement
{
    public static readonly DependencyProperty ItemsProperty =
        DependencyProperty.Register("Items", typeof(IList), typeof(Action), 
                                    new PropertyMetadata(null, null), null);

    public Action()
    {
        this.Items = new ArrayList();
        this.DataContextChanged += (s, e) => MessageBox.Show("Action.DataContext");
    }

    public IList Items
    {
        get { return (IList)this.GetValue(ItemsProperty); }
        set { this.SetValue(ItemsProperty, value); }
    }
}

public class ActionItem : FrameworkElement
{
    public static readonly DependencyProperty DataProperty =
        DependencyProperty.Register("Data", typeof(object), typeof(ActionItem),
            new PropertyMetadata(
                null, null, (d, v) =>
                {
                    if (v != null)
                        MessageBox.Show("ActionItem.Data is not null");
                    return v;
                }
            ), null
        );

    public object Data
    {
        get { return this.GetValue(DataProperty); }
        set { this.SetValue(DataProperty, value); }
    }

    public ActionItem()
    {
        this.DataContextChanged += (s, e) => MessageBox.Show("ActionItem.DataContext");
    }
}

任何想法?

Answer 1

这些项目不是行动控制的儿童,因此数据目录没有传播。你们也许没有什么东西可以纠正。

最简单的办法是压倒一切的行动。采购改变方法,如果财产=e.DataContext 之后,每个行动项目都分配了E. NewValue。这是一个最简单但并非非常好的解决方案,因为如果你在项目清单中增加新的行动,那么它就不会有当前的数据背景。

第二,从项目Control中继承行动,并为之提供海关控制模板。

友情链接