Filter on Array creates document with wrong type

Working with Data Drivers
,
1

Hi, I am trying to filter on an array type, and then perform an upsert.

using MongoDB.Bson;
using MongoDB.Driver;

class MyModel
{
    public ObjectId _id;
    public string[]? myArray;
    public int? myInt;
}
public class UnitTest1
{
    [Fact]
    public async void Test1()
    {
        var client = new MongoClient("mongodb://localhost:27017");
        var database = client.GetDatabase("MyDatabase");
        var collection = database.GetCollection<MyModel>("MyCollection");

        var update = Builders<MyModel>.Update.Set(x => x.myInt, 5);
        var filter = Builders<MyModel>.Filter.AnyEq(x => x.myArray, "not_found");
        var options = new FindOneAndUpdateOptions<MyModel>
        {
            IsUpsert = true,
            ReturnDocument = ReturnDocument.After
        };

        MyModel result = collection.FindOneAndUpdate(filter, update, options); // fails to deserialize
        Assert.IsNotType<string>(result.myArray);
    }
}

Currently it is throwing an error because it seems like it is trying to upsert the document with the “myArray” field set to a string type causing a type mismatch. Can someone explain to me how I can achieve the upsert with the array filter?