Mongo.net - BypassDocumentValidation is not working

Question

I'm trying to insert a json like this (fieldname with a "."), in a Net Core Console Project

{"name.field" : "MongoDB", "type" : "Database"}

Using the C# code belove:

-with InsertManyOptions with BypassDocumentValidation in true

var options = new InsertManyOptions
        {
            BypassDocumentValidation = true,
            IsOrdered = false
        };


        await _collection.InsertManyAsync(items, options);  

But I have this exception:

Element name 'name.field' is not valid

I´m using :

• C# Mongo Driver 2.5
• Net Core Project
• MongoDB version 4.0.3

Any idea? Thanks!

Answer 1

The BypassDocumentValidation can be used to bypass the JSON Schema validation. The issue you are facing, however, is due to the C# driver which explicitly prevents the use of the dot symbol . as part of a field name.

This used to be required up until MongoDB v3.6 which officially added support for fields with ".".

Looking into the internals of the C# driver you can see that the BsonWriter.WriteName method calls contains this code which throws the Exception you're seeing:

if (!_elementNameValidator.IsValidElementName(name))
{
    var message = string.Format("Element name '{0}' is not valid'.", name);
    throw new BsonSerializationException(message);
}

The _elementNameValidator is something that is managed internally by the driver which in fact comes with a NoOpElementNameValidator that doesn't do any validations. The driver, however, won't use this validator for "normal" collections.

All that said, I would strongly advise against the use of field names with "unusual" characters anyway because this is likely to set you up for unexpected behaviour and all sorts of other issues down the road.

In order to get around this you can do one of the following things:

a) Write your own custom serializer which is an option that I would personally steer clear off if possible - it adds complexity that most of the time shouldn't be required.

b) Use the below helper extension (copied from one of the unit testing projects inside the driver) to convert the BsonDocument into a RawBsonDocument which can then successfully written to the server:

public static class RawBsonDocumentHelper
{
    public static RawBsonDocument FromBsonDocument(BsonDocument document)
    {
        using (var memoryStream = new MemoryStream())
        {
            using (var bsonWriter = new BsonBinaryWriter(memoryStream, BsonBinaryWriterSettings.Defaults))
            {
                var context = BsonSerializationContext.CreateRoot(bsonWriter);
                BsonDocumentSerializer.Instance.Serialize(context, document);
            }
            return new RawBsonDocument(memoryStream.ToArray());
        }
    }

    public static RawBsonDocument FromJson(string json)
    {
        return FromBsonDocument(BsonDocument.Parse(json));
    }
}

And then simply write the RawBsonDocument to the server:

RawBsonDocument rawDoc = RawBsonDocumentHelper.FromJson("{\"name.field\" : \"MongoDB\", \"type\" : \"Database\"}");
collection.InsertOne(rawDoc);