.net startup singleton

services startup.cs

   services.AddDbContextPool<dbContext>(options => options.UseSqlite(conn));
            //.UseSqlServer(connection));
            //with scoped
            //services.AddScoped<DmServices>();
            //with singleton
            // services.AddSingleton<DmServices>(s =>
            //  new DmServices(new ProsperusContext(
            //   new DbContextOptionsBuilder<dbContext>().UseSqlite(conn).Options)));
            services.AddSingleton<DmServices>(s =>
                {
                    using (var scope = s.CreateScope())
                    {
                        var dbContext = scope.ServiceProvider.GetService<dbContext>();
                        var lastItem = dbContext;//.Items.LastOrDefault();
                        return new DmServices(lastItem);
                    }
                });