將 MarkupExtension 與轉換器一起使用以跳過資源宣告

通常使用轉換器，我們必須通過以下方式將其定義為資源：

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

通過將轉換器定義為 MarkupExtension 並實現方法 ProvideValue，可以跳過此步驟。以下示例將值轉換為負值：

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;
    }
}
}

使用轉換器：

1. 名稱空間

   xmlns：轉換器= “CLR-名稱空間：MyProject.Converters;裝配= MyProject 的”

2. 示例在繫結中使用此轉換器

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