wpf - 绑定转换器参数

Question

有没有办法我可以做到这一点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>

我只需要将Tag顶级父级和Tag控件本身发送到我的转换器类。

score 340 · Accepted Answer

该ConverterParameter属性无法绑定，因为它不是依赖属性。

因为Binding不是从DependencyObject它的任何属性中派生的都不能是依赖属性。因此，一个 Binding 永远不能成为另一个 Binding 的目标对象。

然而，还有一个替代解决方案。您可以将 aMultiBinding与多值转换器一起使用，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();
    }
}

score 37 · Accepted Answer

不，不幸的是，这是不可能ConverterParameter的，因为不是，DependencyProperty所以您将无法使用绑定

但也许您可以作弊并使用MultiBindingwithIMultiValueConverter来传递 2 个Tag属性。

score 21 · Accepted Answer

还有另一种使用方式MarkupExtension，以便Binding用于ConverterParameter. 使用此解决方案，您仍然可以使用默认值IValueConverter而不是，IMultiValueConverter因为就像您在第一个示例中所期望的那样ConverterParameter传递到。IValueConverter

这是我的可重复使用MarkupExtension：

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

在您的代码库中使用它MarkupExtension，您可以简单地绑定ConverterParameter以下方式：

<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>

这看起来几乎就像你最初的提议。

wpf - 绑定转换器参数

3 回答 3

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