FlexValueConverter.cs

using System;
using System.Text.Json;
using Umbraco.Cms.Core.Models.PublishedContent;
using Umbraco.Cms.Core.PropertyEditors;
using Umbraco.Cms.Core.PropertyEditors.ValueConverters;

namespace DF21
{
    public class FlexValueConverter : PropertyValueConverterBase
    {
        private readonly NestedContentSingleValueConverter _ncValueConverter;

        public FlexValueConverter(NestedContentSingleValueConverter ncValueConverter) => _ncValueConverter = ncValueConverter;

        public override bool IsConverter(IPublishedPropertyType propertyType)
            => propertyType.EditorAlias == "Perplex.Flex";

        public override Type GetPropertyValueType(IPublishedPropertyType propertyType)
            => typeof(IPublishedElement);

        public override object ConvertIntermediateToObject(IPublishedElement owner, IPublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object inter, bool preview)
        {
            if (inter is not string json) return null;
            using var doc = JsonDocument.Parse(json);
            if (!doc.RootElement.TryGetProperty("block", out var block)) return null;
            var rawText = block.GetRawText();
            return _ncValueConverter.ConvertIntermediateToObject(owner, propertyType, referenceCacheLevel, rawText, preview);
        }
    }
}