MongoDB.Bson.Serialization.BsonDefaultSerializationProvider.GetCollectionSerializer C# (CSharp) Метод

        private IBsonSerializer GetCollectionSerializer(Type type)
        {
            Type implementedGenericDictionaryInterface = null;
            Type implementedGenericEnumerableInterface = null;
            Type implementedDictionaryInterface = null;
            Type implementedEnumerableInterface = null;

            var implementedInterfaces = new List<Type>(type.GetInterfaces());
            if (type.IsInterface)
            {
                implementedInterfaces.Add(type);
            }
            foreach (var implementedInterface in implementedInterfaces)
            {
                if (implementedInterface.IsGenericType)
                {
                    var genericInterfaceDefinition = implementedInterface.GetGenericTypeDefinition();
                    if (genericInterfaceDefinition == typeof(IDictionary<,>))
                    {
                        implementedGenericDictionaryInterface = implementedInterface;
                    }
                    if (genericInterfaceDefinition == typeof(IEnumerable<>))
                    {
                        implementedGenericEnumerableInterface = implementedInterface;
                    }
                }
                else
                {
                    if (implementedInterface == typeof(IDictionary))
                    {
                        implementedDictionaryInterface = implementedInterface;
                    }
                    if (implementedInterface == typeof(IEnumerable))
                    {
                        implementedEnumerableInterface = implementedInterface;
                    }
                }
            }

            // the order of the tests is important
            if (implementedGenericDictionaryInterface != null)
            {
                var keyType = implementedGenericDictionaryInterface.GetGenericArguments()[0];
                var valueType = implementedGenericDictionaryInterface.GetGenericArguments()[1];
                var genericSerializerDefinition = typeof(DictionarySerializer<,>);
                var genericSerializerType = genericSerializerDefinition.MakeGenericType(keyType, valueType);
                return (IBsonSerializer)Activator.CreateInstance(genericSerializerType);
            }
            else if (implementedDictionaryInterface != null)
            {
                return new DictionarySerializer();
            }
            else if (implementedGenericEnumerableInterface != null)
            {
                var valueType = implementedGenericEnumerableInterface.GetGenericArguments()[0];
                var readOnlyCollectionType = typeof(ReadOnlyCollection<>).MakeGenericType(valueType);
                Type genericSerializerDefinition;
                if (readOnlyCollectionType.IsAssignableFrom(type))
                {
                    genericSerializerDefinition = typeof(ReadOnlyCollectionSerializer<>);
                    if (type != readOnlyCollectionType)
                    {
                        BsonSerializer.RegisterDiscriminator(type, type.Name);
                    }
                }
                else
                {
                    genericSerializerDefinition = typeof(EnumerableSerializer<>);
                }
                var genericSerializerType = genericSerializerDefinition.MakeGenericType(valueType);
                return (IBsonSerializer)Activator.CreateInstance(genericSerializerType);
            }
            else if (implementedEnumerableInterface != null)
            {
                return new EnumerableSerializer();
            }

            return null;
        }
    }