BsonSerializer - Cannot Deserialize NumberDecimal due to Invalid BspnType error

I have a document with a property of type “object” referring subdocs of different schemas. We are using BsonSerializer to deserialize it, but this class is throwing a BsonInternalException error for subdocs with properties of type decimal: Invalid Bson Type

It looks like decimal deserialization is not supported for decimal types. When should we expect to be supported?

DB Sample

Current: { amount: NumberDecimal(“1”) }

CSharp Sample

Hi, @Daniel_Comanici,

Welcome to the MongoDB Community Forums. I understand that you’re encountering BsonInternalException when trying to deserialize a JSON string containing a decimal. I have reproduced the issue and filed CSHARP-4496.

This bug is due to JsonReader missing support for BsonType.Decimal128. However you don’t need to render the BsonDocument to JSON (which is what ToString() is doing) and then reparse it. You can simply access the BsonDocument.

var bsonDoc = new BsonDocument { { "amount", new Decimal128(42.42m)} };

The return value of the bsonDoc["amount"] is a BsonValue. If you need a specific type, you can call bsonDoc["amount"].AsDecimal. You can also inspect bsonDoc["amount"].BsonType if you need to switch on different types. There are also IsDecimal and other methods to determine if the BsonValue is a particular type.

Hopefully this helps solve your immediate problem. Please follow CSHARP-4496 for the fix to JsonReader.