Ditto `ToList` processor

ToListAttribute.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace Our.Umbraco.Ditto
{
    public class ToListAttribute : DittoProcessorAttribute
    {
        public override object ProcessValue()
        {
            if (typeof(IList).IsAssignableFrom(Context.PropertyDescriptor.PropertyType) && Value is IEnumerable items)
            {
                var targetType = Context.PropertyDescriptor.PropertyType;

                var innerType = targetType.IsGenericType
                    ? targetType.GenericTypeArguments.First()
                    : targetType.IsArray
                        ? targetType.GetElementType()
                        : targetType;

                return (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(innerType), items);
            }

            return Value;
        }
    }
}

ToReadOnlyListAttribute.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace Our.Umbraco.Ditto
{
    public class ToReadOnlyListAttribute : DittoProcessorAttribute
    {
        public override object ProcessValue()
        {
            var targetType = Context.PropertyDescriptor.PropertyType;

            if ((targetType.IsGenericType &&
                targetType.GetGenericTypeDefinition() == typeof(IReadOnlyList<>)) ||
                targetType.GetInterfaces().Any(x => x.IsGenericType &&
                    x.GetGenericTypeDefinition() == typeof(IReadOnlyList<>)))
            {
                var innerType = targetType.IsGenericType
                    ? targetType.GenericTypeArguments.First()
                    : targetType.IsArray
                        ? targetType.GetElementType()
                        : targetType;

                var genericType = typeof(List<>).MakeGenericType(innerType);

                return Value is IEnumerable items
                    ? Activator.CreateInstance(genericType, items)
                    : Activator.CreateInstance(genericType);
            }

            return Value;
        }
    }
}