... using System.Security.Claims; namespace RazorAuthSample.Areas.Identity.Pages.Account { [AllowAnonymous] public class RegisterModel : PageModel { ... public async Task<IActionResult> OnPostAsync(string returnUrl = null) { ... if (ModelState.IsValid) { var user = new IdentityUser { UserName = Input.Email, Email = Input.Email }; var result = await _userManager.CreateAsync(user, Input.Password); if (result.Succeeded) { var claims = new List<Claim> { new Claim("FirstName", Input.FirstName), new Claim("IsAdmin", Input.IsAdmin), }; await _userManager.AddClaimsAsync(user, claims); // To add a single claim // var claim = new Claim("FirstName", Input.FirstName); // await _userManager.AddClaimAsync(user, claim); ... } } // If we got this far, something failed, redisplay form return Page(); } } }