I have a thread in the MongoDB forum for this here: https://www.mongodb.com/community/forums/t/dynamic-variables-are-causing-issues/242663/4

To put the details here; I’m using MongoDB.Driver 2.21.0 in my .NET 7 API. I am trying to use reflection to dynamically return data.

When I use `
Builders<BsonDocument>.Filter.In(field, values)`, if `field` property is a string or int, `values` can be 

new List<dynamic> { "some", "strings", "here" }

 or 

new List<dynamic> { 1, 2, 3 }

 and it correctly returns any documents that contain those values.  But, if `field` is a Guid and `values` is 

new List<dynamic> { Guid.Parse("6cd6f392-8271-49bb-8564-e584ddf48890"), Guid.Parse("c7b1ebaf-4ac1-4fe0-b066-1282e072585a") })

, then I get this error:

MongoDB.Bson.BsonSerializationException: GuidSerializer cannot serialize a Guid when GuidRepresentation is Unspecified.

 
Even though in my Program.cs, I have the Guid representation set.

BsonDefaults.GuidRepresentationMode = GuidRepresentationMode.V3; BsonSerializer.RegisterSerializer(new GuidSerializer(GuidRepresentation.Standard));

If `values` is

new List<Guid> { Guid.Parse("6cd6f392-8271-49bb-8564-e584ddf48890"), Guid.Parse("c7b1ebaf-4ac1-4fe0-b066-1282e072585a") });

It correctly returns any documents that have that Guid in the `field`.  The only difference is `List<dynamic>` vs `List<Guid>`.  But in my case, it needs to be dynamic as I am using input to figure out what documents to filter out.