Why is my Controller being passed a UserManager which is Disposed? - asp.net-core-mvc

Question

When i set a breakpoint in the constructor of this controller, I'm seeing a System.ObjectDisposedException from userManager.Users . Why might .NET be giving me a disposed UserManager? I have other controllers that seem to be set up the same way and their UserManagers work fine (this one dies when it calls GetUserAsync)
[RequireHttps]
public class HomeController : Controller
{
private readonly UserManager<ApplicationUser> _userManager;
private readonly RegionService _regionService;
private readonly ILogger _logger;
public HomeController(UserManager<ApplicationUser> userManager, RegionService regionService, ILoggerFactory loggerFactory)
{
_userManager = userManager;
_regionService = regionService;
_logger = loggerFactory.CreateLogger<HomeController>();
}
[HttpGet]
public async Task<IActionResult> Index()
{
var user = await _userManager.GetUserAsync(HttpContext.User);
...
}
...and i shouldn't be accessing a database in Home/Index; I'll change that afterward
Edit: This is how services are being configured:
public void ConfigureServices(IServiceCollection services)
{
// Add framework services.
services.AddApplicationInsightsTelemetry(Configuration);
services.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
services.AddIdentity<ApplicationUser, IdentityRole>(options =>
{
options.Password.RequireDigit = true;
options.Password.RequireLowercase = false;
options.Password.RequireNonAlphanumeric = false;
options.Password.RequireUppercase = false;
options.Password.RequiredLength = 6;
})
.AddEntityFrameworkStores<ApplicationDbContext>()
.AddDefaultTokenProviders();
services.AddMvc();
// Add application services.
services.AddTransient<IEmailSender, AuthMessageSender>();
services.AddTransient<ISmsSender, AuthMessageSender>();
services.Configure<AuthMessageSenderOptions>(Configuration);
services.AddTransient<RegionService>();
// require SSL
services.Configure<MvcOptions>(options =>
{
options.Filters.Add(new RequireHttpsAttribute());
});
}

Answer 1

The issue was in the constructor of a class I created called RegionService
public RegionService(IServiceProvider serviceProvider)
{
using (var context = serviceProvider.GetService<ApplicationDbContext>())
{
...
}
}
The 'using' statement causes 'context' to be disposed after it's done with that block of code. I should have just been making a new instance of the DbContext that can be disposed:
public RegionService(IServiceProvider serviceProvider)
{
using (var context = new ApplicationDbContext(
serviceProvider.GetRequiredService<DbContextOptions<ApplicationDbContext>>()))
{
...
}
}