所以，我有一个多绑定，其中一个转换器接受一些值并找到它们的最大值。问题是其中一个绑定使用了一个需要double目标类型的转换器，而绑定有一个object目标类型。我想知道是否有任何方法可以修改绑定的目标类型。
下面是我的xaml的近似值：

<TextBlock>
  <TextBlock.Width>
    <MultiBinding Converter="{StaticResource _maxValueConverter}">
      <Binding Source="{StaticResource _constantZeroValue}"/>
      <Binding Path="ActualWidth"
               ElementName="_previousTextBlock"
               Converter="{StaticResource _requiresDoubleTargetConverter}"/>
    </MultiBinding>
  </TextBlock.Width>
</TextBlock>

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所以基本上，如果有任何方法可以告诉第二个绑定它正在输出一个双精度值，那就太好了。
最小可验证完整示例：
MainWindow.xaml个

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        xmlns:local="clr-namespace:WpfApplication1"
        DataContext="{Binding RelativeSource={RelativeSource Self}}"
        Title="MainWindow" Height="350" Width="525">
   <StackPanel>
      <StackPanel.Resources>
         <sys:Double x:Key="constantZero">0</sys:Double>
         <local:RequiresDoubleTargetConverter x:Key="requiresDoubleTargetConverter" />
         <local:MaxValueConverter x:Key="maxValueConverter" />
      </StackPanel.Resources>

      <Border x:Name="topBorder"
              BorderThickness="1"
              BorderBrush="Black"
              HorizontalAlignment="Left">
         <TextBlock x:Name="topTextBlock"
                    Background="Aqua"
                    Text="{Binding TopText}" />
      </Border>

      <Border BorderThickness="1"
              BorderBrush="Black"
              MinWidth="100"
              HorizontalAlignment="Left">
         <TextBlock Background="ForestGreen"
                 Text="{Binding BottomText}"
                 TextWrapping="Wrap"
                 MinWidth="100">
            <TextBlock.Width>

               <MultiBinding Converter="{StaticResource maxValueConverter}">
                  <MultiBinding.Bindings>
                     <Binding Path="ActualWidth" ElementName="topTextBlock" Converter="{StaticResource requiresDoubleTargetConverter}" />
                     <Binding Source="{StaticResource constantZero}" />
                  </MultiBinding.Bindings>
               </MultiBinding>

            </TextBlock.Width>
         </TextBlock>
      </Border>

   </StackPanel>
</Window>

型
MainWindow.xaml.cs个

using System;
using System.Diagnostics;
using System.Globalization;
using System.Windows;
using System.Windows.Data;

namespace WpfApplication1
{
   /// <summary>
   /// Interaction logic for MainWindow.xaml
   /// </summary>
   public partial class MainWindow : Window
   {
      public string TopText
      {
         get { return "Hello World!"; }
      }

      public string BottomText
      {
         get { return "hi earth."; }
      }

      public MainWindow()
      {
         InitializeComponent();
      }
   }

   public class RequiresDoubleTargetConverter : IValueConverter
   {
      public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
      {
         // I am looking for a way to manually ensure that "targetType == typeof(double)" evaluates to true.
         if (targetType != typeof(double))
         {
            return null;
         }
         else
         {
            // Actual converter performs this calculation.
            return (double)value - 14;
         }
      }

      public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
      {
         // Irrelevant method for our purposes.
         throw new NotImplementedException();
      }
   }

   public class MaxValueConverter : IMultiValueConverter
   {
      public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
      {
         double max = double.NegativeInfinity;
         foreach (object value in values)
         {
            if (value is double)
            {
               max = Math.Max((double)value, max);
            }
            else
            {
               Debug.Fail("All values must be doubles");
            }
         }

         return max;
      }

      public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
      {
         // Irrelevant method for our purposes.
         throw new NotImplementedException();
      }
   }
}

型
这是使用Visual Studio 2015创建的，并经过验证以显示错误行为。我试图确定的是是否可以从xaml手动设置RequiresDoubleTargetConverter的targetType。