Account/Company Name: Synergy Sports Technology LLC

Issue + Relevant Info

Customer is getting the following error message in their C# code after upgrading to version 7.0. They are running changeStream and their code requires pre- and post-images (have [changeStreamPreAndPostImages.enabled: true] set)

System.InvalidCastException: Unable to cast object of type 'MongoDB.Bson.BsonNull' to type 'MongoDB.Bson.BsonDocument'.
at MongoDB.Bson.BsonValue.get_AsBsonDocument()
at MongoDB.Driver.ChangeStreamDocument`1.get_FullDocumentBeforeChange()

They are running C# version 2.20.0 and is compatible with 7.0
https://www.mongodb.com/docs/drivers/csharp/current/compatibility/#std-label-csharp-compatibility-tables

Found this Jira that might be related - CSHARP-4745

Portion of customer's code snippets they use for changeStreams:

await database.WatchAsync(pipeline, new ChangeStreamOptions
{
ResumeAfter = token.Token,
FullDocument = ChangeStreamFullDocumentOption.WhenAvailable,
FullDocumentBeforeChange = ChangeStreamFullDocumentBeforeChangeOption.WhenAvailable
}, cancellationToken);

this gets full document from ChangeStreamDocument<BsonDocument> change like this:
var fullDocument = change.FullDocument != default ? change.FullDocument : change.FullDocumentBeforeChange; - this line throws an exception

Requested Action

• Investigate and advise what may be the cause and workaround
• Verify if this is may be related to CSHARP-4745

Status