Question

我有一个用户控件，其中包含Expander和其他一些控件。

用户控件具有自定义“XBackground”属性，该属性实际上仅为Expander设置背景。

    public Brush XBackground
    {
        get
        {
            return expander.Background;
        }
        set
        {
            expander.Background = value;
        }
    }

当我使用我的用户控件时，背景只能静态设置，而不能动态设置。调试器说只能通过动态资源设置DependencyProperty。在这里，我被困住了。我试图在我的XBackground属性上注册依赖属性，但是我收到一条错误，说“只能在DependencyObject的DependencyProperty上设置''DynamicResourceExtension'。”

这是我尝试注册依赖属性：

public static readonly DependencyProperty BcgProperty = DependencyProperty.Register("XBackground", typeof(Brush), typeof(Expander));

Answer 1

轻微错误：

public static readonly DependencyProperty BcgProperty = DependencyProperty.Register（“XBackground”，typeof（Brush），typeof（ YourCustomUserControl ））;

完整版：

public static readonly DependencyProperty XBackgroundProperty 
            = DependencyProperty.Register("XBackground", typeof(Brush), typeof(YourCustomUserControl));
public Brush XBackground
{
    get { return (Brush) GetValue( XBackgroundProperty ); }
    set { SetValue( XBackgroundProperty, value ); }
}

Answer 2

Register中的Owner类不是Expander，而是注册DependencyProperty的类的名称。试试这个：

    public Brush XBackground
    {
        get { return (Brush)GetValue(XBackgroundProperty); }
        set { SetValue(XBackgroundProperty, value); }
    }

    // Using a DependencyProperty as the backing store for XBackground.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty XBackgroundProperty =
        DependencyProperty.Register("XBackground", typeof(Brush), typeof(/typeof your UserControl goes here/), new PropertyMetadata(null));

Answer 3

您不能使用typeof(Expander)，而应使用UserControl的类型作为ownerType方法的Register参数。此外，您还必须在属性包装器中调用GetValue和SetValue。

除此之外，您还必须使用属性元数据注册PropertyChangedCallback，以获得有关属性值更改的通知：

public partial class YourUserControl : UserControl
{
    ...

    public Brush XBackground
    {
        get { return (Brush)GetValue(XBackgroundProperty); }
        set { SetValue(XBackgroundProperty, value); }
    }

    public static readonly DependencyProperty XBackgroundProperty =
        DependencyProperty.Register(
            "XBackground",
            typeof(Brush),
            typeof(YourUserControl),
            new PropertyMetadata(null, XBackgroundPropertyChanged));

    private static void XBackgroundPropertyChanged(
        DependencyObject obj, DependencyPropertyChangedEventArgs e)
    {
        var userControl = (YourUserControl)obj;
        userControl.expander.Background = (Brush)e.NewValue;
    }
}

PropertyChangedCallback的替代方法是将Expander的Background属性绑定到XAML中UserControl的XBackground属性：

<UserControl ...>
    ...
    <Expander Background="{Binding XBackground,
        RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=UserControl}}"/>
    ...
</UserControl>

自定义属性上的WPF动态值

3 个答案: