Creating DbContext ConfigureServices

startup.cs

public void ConfigureServices(IServiceCollection services)  
{
    var connectionString = Configuration["ApplicationDbContext:ConnectionString"];
    services.AddDbContext<ApplicationDbContext>(
        opts => opts.UseNpgsql(connectionString)
    );

    services.Configure<MultitenancyOptions>(  
        options =>
        {
            var scopeFactory = services
                .BuildServiceProvider()
                .GetRequiredService<IServiceScopeFactory>();
    
            using (var scope = scopeFactory.CreateScope())
            {
                var provider = scope.ServiceProvider;
                using (var dbContext = provider.GetRequiredService<ApplicationDbContext>())
                {
                    options.AppTenants = dbContext.AppTenants.ToList();
                }
            }
        });
}