HandyControl/Net35/HandyControl_Net35/Expression/Media/GeometryEffectConverter.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Globalization;

namespace HandyControl.Expression.Media
{
    public sealed class GeometryEffectConverter : TypeConverter
    {
        private static readonly Dictionary<string, GeometryEffect> RegisteredEffects;

        static GeometryEffectConverter()
        {
            var dictionary = new Dictionary<string, GeometryEffect>
            {
                {
                    "None",
                    GeometryEffect.DefaultGeometryEffect
                },
                {
                    "Sketch",
                    new SketchGeometryEffect()
                }
            };
            RegisteredEffects = dictionary;
        }

        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            return typeof(string).IsAssignableFrom(sourceType);
        }

        public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
        {
            return typeof(string).IsAssignableFrom(destinationType);
        }

        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string key && RegisteredEffects.TryGetValue(key, out var effect))
                return effect.CloneCurrentValue();
            return null;
        }

        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value,
            Type destinationType)
        {
            if (typeof(string).IsAssignableFrom(destinationType))
            {
                if (value is string) return value;
                foreach (var pair in RegisteredEffects)
                    if (pair.Value?.Equals(value as GeometryEffect) ?? value == null)
                        return pair.Key;
            }

            return null;
        }
    }
}