I am working on an ASP.NET Core MVC 6 application that uses ASP.NET Core identity and I am facing an issue trying to figure out how to work with the UserManager class.

But UserManager always has null value, I do not know why?
Is ASP.NET Core 6 does not have identity in controllers? and identity scaffolded items are in Razor pages?

This is Code:

public class AccountController : Controller
{
    private ApplicationSignInManager _signInManager;
    private ApplicationUserManager _userManager;

    public BaseController(ApplicationUserManager userManager, ApplicationSignInManager signInManager)
    {
        UserManager = userManager;
        SignInManager = signInManager;
    }

    public ApplicationSignInManager SignInManager
    {
       get
       {
           return _signInManager;
       }
       private set
       {
          _signInManager = value;
       }
   }

   public ApplicationUserManager UserManager
   {
       get
       {
             return _userManager;
       }
       private set
       {
             _userManager = value;
       }
  }


  [HttpPost]
  [AllowAnonymous]
  [ValidateAntiForgeryToken]
  public async Task<ActionResult> Register(RegisterVM model)
  {
      if (ModelState.IsValid)
      {
          var user = new User
          {
              UserName = model.Email,
              Email = model.Email,
              EmailConfirmed = true
          };

          var result = await UserManager.CreateAsync(user, model.Password);

          if (result.Succeeded)
          {
              await SignInManager.SignInAsync(user, isPersistent: false);
              return RedirectToAction("Index", "Home");
          }
          foreach (var error in result.Errors)
          {
              ModelState.AddModelError(string.Empty, error.Description);
          }
      }

    
      return View(model);
  }
}