Bson deserialization error of List with EFCore after application restart

Question

Working with a project in c#, ASP.NET Core with Authentication, MongoDB.Driver and MongoDB.EntityframeworkCore. I'm trying to store a userID as a string in a shopping cart and find the shopping cart using that data. I manage to add items to the cart and when I go to the cart page and call a get-method, it manages to find the cart with no problems. Problem is that if I restart the application, log in with user and go to the cart page again I get the Bson desiralization error:

BsonSerializationException: Unknown discriminator value 'List`1'.

It's when I'm calling the FirstOrDefaultAsync method when I get the deserialization error after I restart the application.

The GetItems code:

public async Task<CartDto> GetItems()
{
    var user = signInManager.Context.User.Identity;
    if (user is not null && user.IsAuthenticated)
    {
        var identity = System.Security.Claims.ClaimTypes.NameIdentifier;
        var userId = signInManager.Context.User.FindFirst(identity)?.Value;

        var userCart = await context.Cart.FirstOrDefaultAsync(c => c.UserId == userId);
        if (userCart is not null)
        {
            CartDto cartDto = new()
            {
                Id = userCart.Id.ToString(),
                UserId = userCart.UserId,
                Products = userCart.Products
            };
            return cartDto;
        }
    }
}

The Cart class, which is stored in MongoDB:

[Collection("Cart")]
public class Cart
{
    public ObjectId Id { get; set; }
    public required string UserId { get; set; }
    public List<string> Products { get; set; }
}

Answer 1

As of version 7.0.0-preview.1, the MongoDB Entity Framework Provider seems to serialize List<T> incorrectly so that the list items are serialized in the following form, instead of serializing plain strings:

{
  // ...
  "Products": {
    "_t": "List`1",
    "_v": [
      "Test1",
      "Test2"
    ]
  }
}

Upon deserialization, the provider expects plain string values in the array, but encounters the _t type discriminator so that an error is raised.

This Jira ticket describes a related issue.