PermissionsService.cs

public class PermissionsService : IPermissionsService
{
  private string _userId;
  private bool _isAdministrator;
  private HttpContext _httpContext;
  private readonly UserManager<BbUser> _userManager;

  public PermissionsService(UserManager<BbUser> userManager)
  {
    _userManager = userManager;
  }

  public async Task<Permissions> GetPermissions(HttpContext httpContext)
  {
    _httpContext = httpContext;
    PopulateUserIdAndIsAdminFlag();
    var permissions = new Permissions
    {
      UserId = _userId,
      IsAdministrator = _isAdministrator
    };

    return await Task.Run(() => permissions);
  }

  private async void PopulateUserIdAndIsAdminFlag()
  {
    if (!IsAuthenticated()) return;
    var username = _httpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);
    var user = await _userManager.FindByNameAsync(username);
    var roles = await _userManager.GetRolesAsync(user);
    _userId = user.Id;
    _isAdministrator = roles.Contains("Admin");
  }

  #region Helper
  private bool IsAuthenticated()
  {
    return _httpContext.User.Identity.IsAuthenticated;
  }
  #endregion
}