基于这个想法(参见publicgk 的回答 https://stackoverflow.com/questions/5524885/nested-binding-and-piped-conversion/5525466#5525466, option C http://www.codeproject.com/KB/WPF/PipingValueConverters_WPF.aspx)可以创建一个转换器,其中包含一组内部按顺序使用的转换器,我编写了一个适合我的需要的劣质实现。即我可以在开始时使用 MultiValueConverter 并将输出通过管道传输到普通转换器列表中:
[ContentProperty("Converters")]
public class GroupConverter : IValueConverter, IMultiValueConverter
{
private IMultiValueConverter _multiValueConverter;
public IMultiValueConverter MultiValueConverter
{
get { return _multiValueConverter; }
set { _multiValueConverter = value; }
}
private List<IValueConverter> _converters = new List<IValueConverter>();
public List<IValueConverter> Converters
{
get { return _converters; }
set { _converters = value; }
}
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return GroupConvert(value, Converters);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return GroupConvertBack(value, Converters.ToArray().Reverse());
}
private static object GroupConvert(object value, IEnumerable<IValueConverter> converters)
{
return converters.Aggregate(value, (acc, conv) => { return conv.Convert(acc, typeof(object), null, null); });
}
private static object GroupConvertBack(object value, IEnumerable<IValueConverter> converters)
{
return converters.Aggregate(value, (acc, conv) => { return conv.ConvertBack(acc, typeof(object), null, null); });
}
#endregion
#region IMultiValueConverter Members
private InvalidOperationException _multiValueConverterUnsetException =
new InvalidOperationException("To use the converter as a MultiValueConverter the MultiValueConverter property needs to be set.");
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
if (MultiValueConverter == null) throw _multiValueConverterUnsetException;
var firstConvertedValue = MultiValueConverter.Convert(values, targetType, parameter, culture);
return GroupConvert(firstConvertedValue, Converters);
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
if (MultiValueConverter == null) throw _multiValueConverterUnsetException;
var tailConverted = GroupConvertBack(value, Converters.ToArray().Reverse());
return MultiValueConverter.ConvertBack(tailConverted, targetTypes, parameter, culture);
}
#endregion
}
(正如你所看到的,我几乎完全忽视了ConverterParameters
, TargetTypes
and CultureInfo
参数,进一步ConvertBack
方法未经测试,所以我不建议任何人实际使用它。)
XAML 用法:
<vc:GroupConverter MultiValueConverter="{StaticResource EqualityComparisonConv}">
<StaticResource ResourceKey="BoolToVisibilityConv"/>
</vc:GroupConverter>