使用标记扩展进行绑定时出错：解析标记扩展时遇到的未知属性 [英] Error when binding using markup extensions: Unknown property encountered while parsing a Markup Extension

问题描述

原则上，我开发了一种简单的方法来将RadioButton绑定到几乎任何东西：

  ///< summary>转换如果它与To属性匹配，则值为true。< / summary> 
 ///< example> 
 ///< RadioButton IsChecked ={Binding VersionString，Converter = {local：TrueWhenEqual To ='1.0'}}/> 
 ///< / example> 
 public class TrueWhenEqual：MarkupExtension，IValueConverter 
 {
 public override object ProvideValue（IServiceProvider serviceProvider）
 {
 return this; 
} 
 
 public object To {get;组; 
 
 public object Convert（object value，Type targetType，object parameter，CultureInfo culture）
 {
 return object.Equals（value，To）; 
} 
 public object ConvertBack（object value，Type targetType，object parameter，CultureInfo culture）
 {
 if（（bool）value）return To; 
抛出新的NotSupportedException（）; 
} 
} 
  

例如，您可以使用它将RadioButtons绑定到一个字符串属性如下（它是一个众所周知的错误，您必须为每个RadioButton使用唯一的GroupName）：

  ; RadioButton GroupName =G1Content =Cat
 IsChecked ={Binding Animal，Converter = {local：TrueWhenEqual To ='CAT'}}/> 
< RadioButton GroupName =G2Content =Dog
 IsChecked ={Binding Animal，Converter = {local：TrueWhenEqual To ='DOG'}}/> 
< RadioButton GroupName =G3Content =Horse
 IsChecked ={Binding Animal，Converter = {local：TrueWhenEqual To ='HORSE'}}/> 
  

现在，我想使用 public static readonly 对象称为 Filter1 和 Filter2 作为我的RadioButtons的值。所以我试过：

 < RadioButton GroupName =F1Content =Filter Number One
 IsChecked = {Binding Filter，Converter = {local：TrueWhenEqual To ='{x：Static local：ViewModelClass.Filter1}'}}/> 
< RadioButton GroupName =F2Content =Filter Number Two
 IsChecked ={Binding Filter，Converter = {local：TrueWhenEqual To ='{x：Static local：ViewModelClass.Filter2} }}/> 
  

但这给我一个错误：

未知属性'to'用于类型
'MS.Internal.Markup.MarkupExtensionParser + UnknownMarkupExtension'
在解析标记扩展时遇到。

如果我删除引号，仍然会出现错误。我做错了什么？

解决方案

这是一个嵌套的MarkupExtensions可能发生的错误。尝试将自定义标记放入单独的DLL / Project或使用属性元素语法。

• http://social.msdn.microsoft.com/Forums/en-US/wpf / thread / 8427e852-0f4f-49b1-9810-28ef6f3bcf09 /




• http：// webcache .googleusercontent.com / search？q = cache：viDdmFIGtq8J：www.hardcodet.net/2008/04/nested-markup-extension-bug+& cd = 1& hl = en& ct = clnk& gl = a>

In principle, I developed a neat way to bind RadioButtons to almost anything:

/// <summary>Converts an value to 'true' if it matches the 'To' property.</summary>
/// <example>
/// <RadioButton IsChecked="{Binding VersionString, Converter={local:TrueWhenEqual To='1.0'}}"/>
/// </example>
public class TrueWhenEqual : MarkupExtension, IValueConverter
{
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }

    public object To { get; set; }

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return object.Equals(value, To);
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if ((bool)value) return To;
        throw new NotSupportedException();
    }
}

For example, you can use this to bind RadioButtons to a string property as follows (it is a well-known bug that you must use a unique GroupName for each RadioButton):

<RadioButton GroupName="G1" Content="Cat"
    IsChecked="{Binding Animal, Converter={local:TrueWhenEqual To='CAT'}}"/>
<RadioButton GroupName="G2" Content="Dog"
    IsChecked="{Binding Animal, Converter={local:TrueWhenEqual To='DOG'}}"/>
<RadioButton GroupName="G3" Content="Horse"
    IsChecked="{Binding Animal, Converter={local:TrueWhenEqual To='HORSE'}}"/>

Now, I would like to use public static readonly objects called Filter1 and Filter2 as the values of my RadioButtons. So I tried:

<RadioButton GroupName="F1" Content="Filter Number One"
    IsChecked="{Binding Filter, Converter={local:TrueWhenEqual To='{x:Static local:ViewModelClass.Filter1}'}}"/>
<RadioButton GroupName="F2" Content="Filter Number Two"
    IsChecked="{Binding Filter, Converter={local:TrueWhenEqual To='{x:Static local:ViewModelClass.Filter2}'}}"/>

But this gives me an error:

Unknown property 'To' for type 'MS.Internal.Markup.MarkupExtensionParser+UnknownMarkupExtension' encountered while parsing a Markup Extension.

The error still occurs if I remove the quotes. What am I doing wrong?

解决方案

It's a bug that can occur with nested MarkupExtensions. Try putting your custom Markup into a separate DLL/Project or use property element syntax.

• http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/8427e852-0f4f-49b1-9810-28ef6f3bcf09/

• http://webcache.googleusercontent.com/search?q=cache:viDdmFIGtq8J:www.hardcodet.net/2008/04/nested-markup-extension-bug+&cd=1&hl=en&ct=clnk&gl=uk

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