Xaml 为什么在尝试将转换器添加到ResourceDictionary时出现此错误？

我尝试将转换器添加到ResourceDictionary，因为我需要使用它，但当我只添加去极化时，在运行应用程序时会出现错误

以下是如何添加转换器声明：

<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"   
xmlns:System="clr-namespace:System;assembly=mscorlib"
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity" 
xmlns:Command="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WP71"
xmlns:converters="clr-namespace:Sample.Utility.Converters">

<converters:BoolToVisibilityConverter x:Key="BoolToVisibilityConverter"/>

我尝试将转换器添加到，但结果相同

有人能帮我解决我的问题吗

---

这是我的转换器的代码

public class BoolToVisibilityConverter : IValueConverter
{
    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool visible = (bool)value;

        return (visible ? Visibility.Visible : Visibility.Collapsed);

    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        Visibility vis = (Visibility)value;
        switch (vis)
        {
            case Visibility.Collapsed:
                return false;
            case Visibility.Visible:
                return true;
        }
        return null;
    }

    #endregion
}

---

要使资源字典在应用程序中全局可用，您需要在

app.xaml中这样合并它：

<Application x:Class="Sample.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/uri/to/resource_dictionary.xaml"/>
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>


能否显示转换器的代码？该转换器类实际上位于
Sample.Utility.Converters
命名空间中？能否尝试将xmlns:Converters=“clr namespace:Sample.Utility.Converters”移动到PhoneApplicationPage或应用程序定义（顶部）或者直接到转换器：BoolToVis xmlns:…？当我将其添加到任何页面或用户控件时，它都会工作，但在ResourceDictionary或App.xaml中都不工作。您知道如何修复它吗？
<Application x:Class="Sample.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="/uri/to/resource_dictionary.xaml"/>
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>