ln.bson/ln.bson/mapper/mappings/ListMapping.cs

using System;
using System.Collections.Generic;

namespace ln.bson.mapper.mappings
{
    public class IListMapping<T, E> : BsonMapping where T : IList<E>
    {
        public IListMapping() : base(typeof(T))
        {
        }

        public override bool TryMapValue(BsonMapper mapper, object o, out BsonValue bsonValue)
        {
            if (mapper.TryGetMapping(typeof(E), out BsonMapping elementMapping))
            {
                BsonArray bsonArray = new BsonArray();
                T source = (T)o;

                foreach (E element in source)
                {
                    if (!elementMapping.TryMapValue(mapper, element, out BsonValue elementValue))
                    {
                        bsonValue = null;
                        return false;
                    }

                    bsonArray.Add(elementValue);
                }

                bsonValue = bsonArray;
                return true;
            }

            bsonValue = null;
            return false;
        }

        public override bool TryMapValue(BsonMapper mapper, BsonValue bsonValue, out object o)
        {
            if (bsonValue is BsonArray bsonArray && mapper.TryGetMapping(typeof(T), out BsonMapping elementMapping))
            {
                T destinationList = Activator.CreateInstance<T>();

                for (int i = 0; i < bsonArray.Length; i++)
                {
                    if (!elementMapping.TryMapValue(mapper, bsonArray[i], out object element))
                    {
                        o = null;
                        return false;
                    }

                    destinationList.Add((E)element);
                }

                o = destinationList;
                return true;
            }

            o = null;
            return false;
        }
    }
}