将 MarkupExtension 与转换器一起使用以跳过资源声明

通常使用转换器，我们必须通过以下方式将其定义为资源：

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

通过将转换器定义为 MarkupExtension 并实现方法 ProvideValue，可以跳过此步骤。以下示例将值转换为负值：

namespace MyProject.Converters
{
public class Converter_Negative : MarkupExtension, IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return this.ReturnNegative(value);
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return this.ReturnNegative(value);
    }

    private object ReturnNegative(object value)
    {
        object result = null;
        var @switch = new Dictionary<Type, Action> {
            { typeof(bool), () => result=!(bool)value },
            { typeof(byte), () => result=-1*(byte)value },
            { typeof(short), () => result=-1*(short)value },
            { typeof(int), () => result=-1*(int)value },
            { typeof(long), () => result=-1*(long)value },
            { typeof(float), () => result=-1f*(float)value },
            { typeof(double), () => result=-1d*(double)value },
            { typeof(decimal), () => result=-1m*(decimal)value }
        };

        @switch[value.GetType()]();
        if (result == null) throw new NotImplementedException();
        return result;
    }

    public Converter_Negative()
        : base()
    {
    }

    private static Converter_Negative _converter = null;

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (_converter == null) _converter = new Converter_Negative();
        return _converter;
    }
}
}

使用转换器：

1. 命名空间

   xmlns：转换器= “CLR-名称空间：MyProject.Converters;装配= MyProject 的”

2. 示例在绑定中使用此转换器

   <RichTextBox IsReadOnly="{Binding Path=IsChecked, ElementName=toggleIsEnabled, Converter={converters:Converter_Negative}}"/>