c# - WPF:BindingExpression 产生的值对目标无效

Question

无法解决这个问题，我正在努力使这个模板尽可能多才多艺。尝试将 TextBlock 居中时出现以下错误，Horizo​​ntalAlignment 不起作用。

System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='0' BindingExpression:Path=ActualWidth; DataItem='Grid' (Name='PathGrid'); target element is 'TextBlock' (Name='PathPercentage'); target property is 'FontSize' (type 'Double')

System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='-6 -6 -6 -6' MultiBindingExpression:target element is 'TextBlock' (Name='PathPercentage'); target property is 'Margin' (type 'Thickness')

System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='-17 -17 -17 -17' MultiBindingExpression:target element is 'TextBlock' (Name='PathPercentage'); target property is 'Margin' (type 'Thickness')

System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='83 83 83 83' MultiBindingExpression:target element is 'TextBlock' (Name='PathPercentage'); target property is 'Margin' (type 'Thickness')

这是带有我的绑定(bind)的 ControlTemplate

<Grid x:Name="PathGrid" Margin="2" Width="200">
                        <Canvas>
                            <TextBlock x:Name="PathPercentage" Text="{Binding RelativeSource={RelativeSource TemplatedParent},Path=Value}"
                                       Foreground="White"
                                       FontSize="{Binding ElementName=PathGrid, Path=ActualWidth, Converter={StaticResource SizeTextOnParent}}">
                                <TextBlock.Margin>
                                    <MultiBinding Converter="{StaticResource CenterElement}">
                                        <Binding ElementName="PathGrid" Path="ActualWidth"/>
                                        <Binding ElementName="PathPercentage" Path="FontSize"/>
                                    </MultiBinding>
                                </TextBlock.Margin>
                            </TextBlock>
                            <TextBlock Text="{Binding ElementName=PathPercentage, Path=Margin}" />
                            <Ellipse Fill="Transparent" 
                                 Stroke="#434953" 
                                 StrokeThickness="3" 
                                 Width="{Binding ElementName=PathGrid, Path=ActualWidth}" 
                                 Height="{Binding ElementName=PathGrid, Path=ActualWidth}" />

这是我的转换器，它应该产生将我的文本 block 居中的边距值:

using System;
using System.Globalization;
using System.Linq;
using System.Windows;
using System.Windows.Data;

namespace Test_Project.Converters
{
    public class CenterElement : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            double parentWidth = (double)values[0];
            double fontSize = (double)values[1];

            double t = Math.Round(((parentWidth / 2) - (fontSize / 2)), 0);
            string margin = t + " " + t + " " + t + " " + t;

            return margin;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}

Answer 1

哎呀，设法修复它。只需确保它返回类型 Thickness。我假设它应该返回 Margin 作为一种类型，这就是我努力寻找它的原因!

double t = Math.Round(((parentWidth / 2) - (fontSize / 2)), 0);
            Thickness margin = new Thickness(t, t, t, t);

            return margin;