ln.bson/ln.bson/mapper/mappings/DictionaryMapping.cs

using System;
using System.Collections.Generic;
using System.Text.Json;

namespace ln.bson.mapper.mappings
{
    public class DictionaryMapping<T> : BsonMapping
    {
        public DictionaryMapping() : base(typeof(Dictionary<string,T>))
        {
        }

        public override bool TryMapValue(BsonMapper mapper, object o, out BsonValue bsonValue)
        {
            if (mapper.TryGetMapping(typeof(T), out BsonMapping elementMapping))
            {
                Dictionary<string, T> d = (Dictionary<string, T>)o;
                BsonDocument bsonDocument = new BsonDocument();

                foreach (KeyValuePair<string, T> keyValuePair in d)
                {
                    if (!elementMapping.TryMapValue(mapper, keyValuePair.Value, out BsonValue elementValue))
                    {
                        bsonValue = null;
                        return false;
                    }
                    bsonDocument.Add(keyValuePair.Key, elementValue);
                }
                
                bsonValue = bsonDocument;
                return true;
            }
            bsonValue = null;
            return false;

        }

        public override bool TryMapValue(BsonMapper mapper, BsonValue bsonValue, out object o)
        {
            if (bsonValue is BsonDocument bsonDocument && mapper.TryGetMapping(typeof(T), out BsonMapping elementMapping))
            {
                Dictionary<string, T> d = new Dictionary<string, T>();

                foreach (KeyValuePair<string,BsonValue> keyValuePair in bsonDocument)
                {
                    if (!elementMapping.TryMapValue(mapper, keyValuePair.Value, out object element))
                    {
                        o = null;
                        return false;
                    }
                    d.Add(keyValuePair.Key, (T)element);
                }

                o = d;
                return true;
            }

            o = null;
            return false;
        }
    }
}