如何创建接受多个值并序列化为 WinForms Form.designer.cs 的 TypeConverter？ [复制]

我有一个抽象类，它有两个子类。值、StringValue 或 CustomValue。我想创建一个转换器来接受选择我需要的类并对其进行良好的序列化。

有一个question https://stackoverflow.com/questions/37931785/winforms-designer-properties-of-different-derived-types/37935544?noredirect=1#comment119779013_37935544答案非常好（但让我添加更多行以确保它接受空值）

A型转换器

 public class ValueConverter: SortedExpandableObjectConverter
    {
        private Value[] standardValues = new Value[3] { null, new StringValue(), new CustomValue()};
        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
        {
            if (sourceType == typeof(string)) return true;
            return base.CanConvertFrom(context, sourceType);
        }
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            switch (value.ToString().Replace(" ", ""))
            {
                case "(None)":
                    return null;
                case nameof(StringValue):
                    return new StringValue();
                case nameof(CustomValue):
                    return new CustomValue();
            }
            return base.ConvertFrom(context, culture, value);
        }
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (value == null) return "(None)"; // to accept null value.
            return base.ConvertTo(context, culture, value, destinationType);
        }
        public override StandardValuesCollection GetStandardValues(ITypeDescriptorContext context) => new StandardValuesCollection(standardValues);
        public override bool GetStandardValuesSupported(ITypeDescriptorContext context) => true;
        public override bool GetStandardValuesExclusive(ITypeDescriptorContext context) => true;
    }

A类

[TypeConverter(typeof(ValueConverter))]
public abstract class Value{}

public class StringValue : Value{ properties...}
public class CustomValue : Value{properties...}

   In UserControl declare property: 
   [DefaultValue(null)] // Is must for display null as grayed
   public Value MyValue{get;set;}