How to use decimal type in MongoDB

Question

How can I store decimals in MongoDB using the standard C# driver? It seems that all decimals are stored inside the database as strings.

Answer 1

I had issues using the RegisterSerializer approach as it complained that it already had a serializer registered, but an alternative is to write your own serialization provider and use that.

Here's the provider:

public class CustomSerializationProvider : IBsonSerializationProvider
{
    private static readonly DecimalSerializer DecimalSerializer = new DecimalSerializer(BsonType.Decimal128);
    private static readonly NullableSerializer NullableSerializer = new NullableSerializer(new DecimalSerializer(BsonType.Decimal128));

    public IBsonSerializer GetSerializer(Type type)
    {
        if (type == typeof(decimal)) return DecimalSerializer;
        if (type == typeof(decimal?)) return NullableSerializer;

        return null; // falls back to Mongo defaults
    }
}

which you need to register by calling

BsonSerializer.RegisterSerializationProvider(new CustomSerializationProvider());