Refer to a table in another database on the same server

Question

I’m making an app on C# and .NET Core (ASP.NET Core MVC) using the EntityFrameworkCore and in the Connection String access to a database, say DB1, and I can read the tables in this database programmatically.

The string Connection is:

Server=MY\\SQLEXPRESS;Initial Catalog=DB1;User ID=Me;
    Persist Security Info=True;Integrated Security=SSPI;

But on the same server I have other databases, say DB2. In my app I needed to access both databases. So the code of the Model is:

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace MyApp.Models
{
    // modelo das várias tabelas na DB1...

    [Table("tMyTable")]      // esta tabela está na DB2!
    public class MyModel
    {
        [Key]
        public int ID { get; set; }
        // ...
    }
}

The data access model is:

using System.Linq;
using Microsoft.EntityFrameworkCore;

public class appDataContext : DbContext
{
    private AppFeatures features { get; set; }

    private DbContextOptions<appDataContext> opt { get; set; }

    private DbSet<MyModel> tbl { get; set; }

    public appDataContext(
        DbContextOptions<appDataContext> options, 
        AppFeatures _features 
    )
        : base(options)
    {
        opt = options;
        features = _features;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder.UseSqlServer(features.ConnectionString);

    private IEnumerable<MyModel> _fcRetrieveUser(int id)
        => tbl.Where(l => l.ID == id);

    // acesso a outras tabelas
}

Of course this code does not work, because the tMyTable is not pointed at the Connection String, how can I refer to this table in the correct database without creating another Connection String and using this skeleton, and without using pure SQL (Raw SQL)?

I’ve tried to put [Table("DB2.dbo.tMyTable")] or [Table("tMyTable", Schema="DB2.dbo")] but none worked.

Is there an attribute you can use to refer to the database DB2, as an example Database?