Serialize entity class containing IMongoQuery

Question

My entity class is like this:

public class MyType
{
    public string Name { get; set; }
    public IMongoQuery MyQuery { get; set; }
}

I am not able to persist this with the default serializers, when MyQuery contains anything complex such as an $in.

BsonDocumentSerializer gives error:

 Element name '$in' is not valid because it starts with a '$'.

I assume I need a special serializer type attributed to MyQuery. I've tried BsonDocument, BsonString, BsonJavaScript - all cannont cast to MongoDB.Driver.QueryDocument, which is the type of object stored in MyQuery.

Does this require a custom IBsonSerializer?

Answer 1

This seems to work. Stores the query as a JSON string.

public class QueryDocumentSerializer : BsonBaseSerializer
    {
        public override object Deserialize(MongoDB.Bson.IO.BsonReader bsonReader, Type nominalType, Type actualType, IBsonSerializationOptions options)
        {
            if (bsonReader.GetCurrentBsonType() == BsonType.Null)
            {
                bsonReader.ReadNull();
                return null;
            }
            else
            {
                var value = bsonReader.ReadString();
                var doc = BsonDocument.Parse(value);
                var query = new QueryDocument(doc);
                return query;
            }
        }

        public override void Serialize(MongoDB.Bson.IO.BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
        {
            if (value == null)
            {
                bsonWriter.WriteNull();
            }
            else
            {
                var query = (QueryDocument)value;
                var json = query.ToJson();
                bsonWriter.WriteString(json);
            }
        }
    }