Using EF and SqLite - keep getting "object reference not set to an instance of an object"

I'm sure this will be a simple fix to a trained eye, but apparently my eyes are not trained enough...

I'm using Xamarin.Forms .Netstandard 2.0 project with EF and SQLite. I am able to: create database, put data into database. I am unable to: get data OUT of database.

• I have the plumbing code in Android and iOS projects which obtain the proper path to the "db3" file. I pass that path to the app.xaml.cs and set that to a static var so it's available everywhere.

• I have a class which inherits from "DbContext". In it is a "DbSet Cats {get; set;}" statement. The constructor accepts the path and calls the "Database.EnsureCreatedAsync()". I know this works, I can ADB pull the db and all tables are created.

• I can use the context and "add" and "savechanges" to put data into the db. This works, I've confirmed the data are in there.

• when I go to query the db, I've tried everything and keep getting this error, object reference....

I don't see any "dbConnection" code per se. I have in my context class the "onConfiguring" method and have confirmed it gets the right db path.

I've scoured the web and the examples. I think I have all the pieces, but obviously something is missing or done incorrectly. Here's some code:

public class DatabaseContext : DbContext
{
string _dbPath;

    public DbSet<Cat> Cats { get; set; }

    public DatabaseContext(string dbPath)
    {
        _dbPath = dbPath;

        Database.EnsureCreatedAsync();
    }

    public async Task<IEnumerable<Cat>> GetCats()
    {
        var allCats = await Cats.ToListAsync().ConfigureAwait(false);

        return allCats;
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlite($"Filename={_dbPath}");
    }
}


List<Cat> itemSource;

// Create Database & Tables
using (var db = new DatabaseContext(App.dbPath))
{
    // Ensure database is created
    db.Database.EnsureCreated();

    // Insert Data
    db.Add(new Cat() { IdCat = "111", Fname = "Felix1" });
    db.SaveChanges();

    // Retreive Data

    //method 1
    // RESULT:  no data are in "itemsource", info reads "exception count = 1"
    itemSource = db.Cats.ToList();

    // method 2
    // RESULTS:  crashes with error "System.NullReferenceException: Object reference not set to an instance of an object."
    Task<IEnumerable<Cat>> p = db.GetCats();    

    itemSource = db.Cats.ToList();
}