Binding ConverterParameter

Question

我是否可以在Style:

<Style TargetType="FrameworkElement">
    <Setter Property="Visibility">
        <Setter.Value>
            <Binding Path="Tag"
                RelativeSource="{RelativeSource AncestorType=UserControl}"
                Converter="{StaticResource AccessLevelToVisibilityConverter}"
                ConverterParameter="{Binding RelativeSource={RelativeSource Mode=Self}, Path=Tag}" />                        
        </Setter.Value>
    </Setter>
</Style>

我只需要发送顶级父的Tag和控件本身的Tag到我的转换器类。

Answer 1

ConverterParameter属性不能被绑定，因为它不是一个依赖属性。

因为Binding不是从DependencyObject派生出来的，所以它的属性不能是依赖属性。因此，一个Binding永远不能成为另一个Binding的目标对象。

然而，有一个替代的解决方案。您可以使用带有多值转换器的MultiBinding，而不是普通的Binding:

<Style TargetType="FrameworkElement">
    <Setter Property="Visibility">
        <Setter.Value>
            <MultiBinding Converter="{StaticResource AccessLevelToVisibilityConverter}">
                <Binding Path="Tag" RelativeSource="{RelativeSource Mode=FindAncestor,
                                                     AncestorType=UserControl}"/>
                <Binding Path="Tag" RelativeSource="{RelativeSource Mode=Self}"/>
            </MultiBinding>
        </Setter.Value>
    </Setter>
</Style>

多值转换器获取源值数组作为输入:

public class AccessLevelToVisibilityConverter : IMultiValueConverter
{
    public object Convert(
        object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        return values.All(v => (v is bool && (bool)v))
            ? Visibility.Visible
            : Visibility.Hidden;
    }
    public object[] ConvertBack(
        object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

Answer 2

不，不幸的是，这是不可能的，因为ConverterParameter不是DependencyProperty，所以你将无法使用绑定

但也许你可以欺骗和使用MultiBinding与IMultiValueConverter传递在2 Tag属性。

Answer 3

还有另一种使用MarkupExtension的方法，以便为ConverterParameter使用Binding。使用此解决方案，您仍然可以使用默认的IValueConverter而不是IMultiValueConverter，因为ConverterParameter被传递到IValueConverter中，就像您在第一个示例中所期望的那样。

这是我可重复使用的MarkupExtension:

/// <summary>
///     <example>
///         <TextBox>
///             <TextBox.Text>
///                 <wpfAdditions:ConverterBindableParameter Binding="{Binding FirstName}"
///                     Converter="{StaticResource TestValueConverter}"
///                     ConverterParameter="{Binding ConcatSign}" />
///             </TextBox.Text>
///         </TextBox>
///     </example>
/// </summary>

[ContentProperty(nameof(Binding))]
public class ConverterBindableParameter : MarkupExtension
{
    #region Public Properties
    public Binding Binding { get; set; }
    public BindingMode Mode { get; set; }
    public IValueConverter Converter { get; set; }
    public Binding ConverterParameter { get; set; }
    #endregion
    public ConverterBindableParameter()
    { }
    public ConverterBindableParameter(string path)
    {
        Binding = new Binding(path);
    }
    public ConverterBindableParameter(Binding binding)
    {
        Binding = binding;
    }
    #region Overridden Methods
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        var multiBinding = new MultiBinding();
        Binding.Mode = Mode;
        multiBinding.Bindings.Add(Binding);
        if (ConverterParameter != null)
        {
            ConverterParameter.Mode = BindingMode.OneWay;
            multiBinding.Bindings.Add(ConverterParameter);
        }
        var adapter = new MultiValueConverterAdapter
        {
            Converter = Converter
        };
        multiBinding.Converter = adapter;
        return multiBinding.ProvideValue(serviceProvider);
    }
    #endregion
    [ContentProperty(nameof(Converter))]
    private class MultiValueConverterAdapter : IMultiValueConverter
    {
        public IValueConverter Converter { get; set; }
        private object lastParameter;
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (Converter == null) return values[0]; // Required for VS design-time
            if (values.Length > 1) lastParameter = values[1];
            return Converter.Convert(values[0], targetType, lastParameter, culture);
        }
        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            if (Converter == null) return new object[] { value }; // Required for VS design-time
            return new object[] { Converter.ConvertBack(value, targetTypes[0], lastParameter, culture) };
        }
    }
}

在你的代码库中有了这个MarkupExtension，你可以简单地用下面的方式绑定ConverterParameter:

<Style TargetType="FrameworkElement">
<Setter Property="Visibility">
    <Setter.Value>
     <wpfAdditions:ConverterBindableParameter Binding="{Binding Tag, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}"
                 Converter="{StaticResource AccessLevelToVisibilityConverter}"
                 ConverterParameterBinding="{Binding RelativeSource={RelativeSource Mode=Self}, Path=Tag}" />          
    </Setter.Value>
</Setter>

看起来和你最初的提议差不多