Hi everyone,
It seems that casting via the IVehicle interface is not supported in LinqProvider.V3.
When attempting to filter based on a field inside a discriminated subtype, the following query fails:
var user = await collection.Find(x => ((Car)x.Vehicle!).Model == "Test").FirstOrDefaultAsync();
This throws the following exception:
MongoDB.Driver.Linq.ExpressionNotSupportedException : Expression not supported: Convert(x.Vehicle, Car)
because conversion to MongoCases.MongoNestedDiscriminatedUnionCases+Car is not supported.
However, this exact code worked fine in LinqProvider.V2. After upgrading to LinqProvider.V3, the query no longer functions as expected.
Additionally, if I replace IVehicle (an interface) with a regular class, everything works fine. Unfortunately, changing IVehicle to a class is not an option for my case.
Is there a way to make this work while keeping IVehicle as an interface?
Any suggestions or workarounds would be greatly appreciated!
Full Reproduction Code:
using System;
using System.Threading.Tasks;
using MongoDB.Bson;
using MongoDB.Bson.Serialization;
using MongoDB.Bson.Serialization.Attributes;
using MongoDB.Bson.Serialization.Serializers;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using NUnit.Framework;
namespace MongoCases
{
[TestFixture]
public class MongoNestedDiscriminatedUnionCases : Mongo2GoFixture
{
[Test]
public async Task Test()
{
BsonSerializer.RegisterSerializer(new ObjectSerializer(_ => true));
var mongoClientSettings = MongoClientSettings.FromConnectionString(ConnectionString);
mongoClientSettings.LinqProvider = LinqProvider.V3;
var mongoClient = new MongoClient(mongoClientSettings);
var db = mongoClient.GetDatabase(Guid.NewGuid().ToString().Substring(0, 8));
var collection = db.GetCollection<User>("users");
await collection.InsertOneAsync(new User());
await collection.InsertOneAsync(new User { Vehicle = new Car { Model = "Test" } });
var user = await collection.Find(x => ((Car)x.Vehicle!).Model == "Test").FirstOrDefaultAsync();
// MongoDB.Driver.Linq.ExpressionNotSupportedException : Expression not supported: Convert(x.Vehicle, Car)
// because conversion to MongoCases.MongoNestedDiscriminatedUnionCases+Car is not supported.
Assert.That(user, Is.Not.Null);
}
private class User
{
[BsonId] public ObjectId Id { get; set; }
[BsonElement("vehicle"), BsonIgnoreIfNull]
public IVehicle? Vehicle { get; set; }
}
private interface IVehicle
{
}
[BsonDiscriminator("car")]
private class Car : IVehicle
{
[BsonElement("model"), BsonRequired]
public string Model { get; set; }
}
[BsonDiscriminator("bike")]
private class Bike : IVehicle
{
}
}
}