Brush IValueConverter的枚举在尝试强制转换System时引发异常.字符串到IValueConvert

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

我的列举(并非真正相关)：

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，我试图使用它来根据枚举的值更改标签的颜色(color是Colors类型的公共属性)：

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

当构建窗口时，我得到以下异常：

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:UsersstevezDocumentsVisual Studio 2010ProjectsTestCollectionChangingListboxTestCollectionChangingListboxMainWindow.xaml:line 1
at TestCollectionChangingListbox.MainWindow..ctor() in C:UsersstevezDocumentsVisual Studio 2010ProjectsTestCollectionChangingListboxTestCollectionChangingListboxMainWindow.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}}" />

Answer 2

您需要在相关控件的resources部分创建该转换器的实例(如果您想在应用程序中的多个位置使用转换器，则可以在app.xaml文件中创建)：

<UserControl.Resources>
<local:EnumToBrushConverter x:Key="EnumToBrushConverter " />
</UserControl.Resources>

然后将该转换器引用为静态资源：

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