ln.bson/ln.bson/mapper/mappings/ArrayMapping.cs

using System;

namespace ln.bson.mapper.mappings
{
    public class ArrayMapping<T> : BsonMapping
    {
        public ArrayMapping() : base(typeof(T[]))
        {
        }

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

                foreach (T element in sourceArray)
                {
                    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[] destinationArray = new T[bsonArray.Length];

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

                    destinationArray[i] = (T)element;
                }

                o = destinationArray;
                return true;
            }

            o = null;
            return false;
        }
    }
}