wpf - 枚举到 Brush IValueConverter 尝试将 System.String 转换为 IValueConverter 时抛出异常？

Question

我正在尝试将枚举转换为画笔，以便可以使用枚举变量来控制某些控件的颜色

我的枚举(并不真正相关):

public enum Colors {
        Red, Blue,
    }

这是我的转换器:

[ValueConversion(typeof(Colors), typeof(Brush))]
public class EnumToBrushConverter : IValueConverter {

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        return (Brushes.Red);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        throw new NotImplementedException();
    }
}

在这里，我尝试使用它根据枚举的值更改标签的颜色(Color 是 Colors 类型的公共(public)属性):

<Grid>
    <Grid.Resources>
        <conv:EnumToBrushConverter x:Key="EnumToBrushConverter" />
    </Grid.Resources>
    <Label Content="fixed" Foreground="{Binding Path=Color, Converter=EnumToBrushConverter}" />
</Grid>

构造窗口时，出现以下异常:

System.Windows.Markup.XamlParseException occurred
  Message='Set property 'System.Windows.Data.Binding.Converter' threw an exception.' Line number '9' and line position '11'.
  Source=PresentationFramework
  LineNumber=9
  LinePosition=11
  StackTrace:
       at System.Windows.Markup.XamlReader.RewrapException(Exception e, IXamlLineInfo lineInfo, Uri baseUri)
       at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
       at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
       at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
       at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
       at TestCollectionChangingListbox.MainWindow.InitializeComponent() in c:\Users\stevez\Documents\Visual Studio 2010\Projects\TestCollectionChangingListbox\TestCollectionChangingListbox\MainWindow.xaml:line 1
       at TestCollectionChangingListbox.MainWindow..ctor() in C:\Users\stevez\Documents\Visual Studio 2010\Projects\TestCollectionChangingListbox\TestCollectionChangingListbox\MainWindow.xaml.cs:line 29
  InnerException: System.InvalidCastException
       Message=Unable to cast object of type 'System.String' to type 'System.Windows.Data.IValueConverter'.
       Source=PresentationFramework
       StackTrace:
            at System.Windows.Baml2006.WpfSharedBamlSchemaContext.<Create_BamlProperty_Binding_Converter>b__14c(Object target, Object value)
            at System.Windows.Baml2006.WpfKnownMemberInvoker.SetValue(Object instance, Object value)
            at MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue(XamlMember member, Object obj, Object value)
            at MS.Internal.Xaml.Runtime.ClrObjectRuntime.SetValue(Object inst, XamlMember property, Object value)
       InnerException: 

Answer 1

您需要将转换器作为静态资源进行访问；试试这个:

<Label Content="fixed" Foreground="{Binding Path=Color, Converter={StaticResource EnumToBrushConverter}}" />