You could use SQLite-Net Extensions to achieve this function, Add a Foreign key in the Product class.

Here is running GIF about your project.First of all, I use “12” account to login in, here are several records in the product page. Then I restart your application, to create new account called “34”, when I log in, it have new shopping list, you can add product to the pages.

I changed Product like following code.

   public class Product
    {
        [PrimaryKey, AutoIncrement]
        public int ID { get; set; }
        public string Name { get; set; }
        public string Notes { get; set; }
        public bool Bought { get; set; }

        [ForeignKey(typeof(User))] 
        public int UserId { get; set; }

        [ManyToOne]      // Many to one relationship with Stock
        public User User { get; set; }
    }

I changed User like following code.

    public class User
    {
        [PrimaryKey, AutoIncrement]
        public int ID { get; set; }
        public string Username { get; set; }

        public string Password { get; set; }

        public string Email { get; set; }

        [OneToMany(CascadeOperations = CascadeOperation.All)]
        public List<Product> Products { get; set; }
    }

If you want to insert the data to Product table. You should change Add event like following code.

            saveButton.Clicked += async (sender, e) =>
            {
                var product = (Product)BindingContext;

                await App.ProductDataBase.SaveItemAsync(product);


                //check the data
                var products = App.ProductDataBase.GetItemsAsync();
                var usersFrst = UserDatabase.Database.GetWithChildren<User>(user.ID);

                if (user.Products == null)
                {
                    user.Products = new List<Product>() { product };

                }
                else
                {

                    user.Products.Add(product);
                }

                //Update the changes into the database 

                UserDatabase.Database.UpdateWithChildren(user);

               await Navigation.PopAsync();
            };

When U login by new account, you should transfer User object. I update your demo, you can download it and test it.

https://github.com/851265601/Xamarin.Android_ListviewSelect/blob/master/shopper.zip

I’m developing shopping list app with Xamarin and SQlite and I struggle with one problem. I have 2 tables – Users and Products. Registration and login work fine but the problem is how to serve a new empty shopping list. For now, it doesn’t matter on which user I’m logged in, it always shows the same list.
I don’t know exactly which part of code should I paste here so here is a repository: https://github.com/przezro098/Shopper.