UserManager<T> is the ASP.NET Core Identity service for working with user accounts. It can create accounts, load users from the database, change passwords, and add claims. SignInManager<T> handles signing users in and out, while UserManager<T> handles much of the account data and credential work. section 23.7
A registration handler typically creates an ApplicationUser, supplies the password to CreateAsync, and checks the result. After a successful creation, AddClaimAsync can attach application data such as a FullName claim. Claims become available through HttpContext.User after sign-in. section 23.6 section 23.7
Add a claim during registration
Create the user with _userManager.CreateAsync(user, Input.Password), then create new Claim("FullName", Input.Name) and pass it to _userManager.AddClaimAsync(user, claim). The handler can then generate an email-confirmation token and send the confirmation message. Later, display the value with User.FindFirstValue("FullName"). section 23.6
UserManager<T> supplies the service layer, not the complete user interface. The application must provide or enable the pages and endpoints, protect permission-editing pages appropriately, and configure Identity features such as email confirmation or multifactor authentication when needed. section 23.6 section 23.7
