public class Order
{
    public int Id { get; set; }
    public double TotalAmount { get; set; }
    public IdentityUser UserAccount { get; set; }
    public virtual ICollection<OrderProduct> OrderProduct { get; set; }
    public DateTime OrderDate { get; set; }
    public bool IsComplete { get; set; }
}

public class OrderProduct
{
    public int Id { get; set; }
    public Order Order { get; set; }
    public Product Product { get; set; }
    public int Quantity { get; set; }
}