Add claims on successful login and retrieve it elsewhere in the application

You must add your claims before login not after. Consider this example:

public async Task<ActionResult> Login(LoginViewModel model,string returnUrl){    var user = UserManager.Find(model.Email, model.Password);    if(user!=null)    {        var ident = UserManager.CreateIdentity(user,             DefaultAuthenticationTypes.ApplicationCookie);        ident.AddClaims(new[] {            new Claim("MyClaimName","MyClaimValue"),            new Claim("YetAnotherClaim","YetAnotherValue"),        });        AuthenticationManager.SignIn(            new AuthenticationProperties() { IsPersistent = true },             ident);        return RedirectToLocal(returnUrl);    }    ModelState.AddModelError("", "Invalid login attempt.");    return View(model);}

Now since we have injected our claims while signing in, we have access to claims wherever we want:

((ClaimsIdentity)User.Identity).FindFirst("MyClaimName");

Also you could add your claims in ApplicationUser.GenerateUserIdentityAsync() method. By adding your claims in this method you could use SignInManager.PasswordSignInAsync() method to sign in users without any modification to default Login action method.

public class ApplicationUser : IdentityUser{    public async Task<ClaimsIdentity> GenerateUserIdentityAsync(UserManager<ApplicationUser> manager)    {        var userIdentity = await manager.CreateIdentityAsync(this, DefaultAuthenticationTypes.ApplicationCookie);        // Add custom user claims here        userIdentity .AddClaims(new[] {            new Claim("MyClaimName","MyClaimValue"),            new Claim("YetAnotherClaim","YetAnotherValue"),        });        return userIdentity;    }}

In identity 2, this is done very differently and simply by creating a claims principal factory and then hooking it up in your startup ConfigureServices as below...

public class CustomClaimsPrincipalFactory : UserClaimsPrincipalFactory<IUser, IApplicationRole>{    public CustomClaimsPrincipalFactory(UserManager<IUser> userManager, RoleManager<IApplicationRole> roleManager,                                                IOptions<IdentityOptions> optionsAccessor)        : base(userManager, roleManager, optionsAccessor)    {    }    public async override Task<ClaimsPrincipal> CreateAsync(IUser user)    {        var principal = await base.CreateAsync(user);        // Add your claims here        ((ClaimsIdentity)principal.Identity).AddClaims(new[] { new Claim(ClaimTypes.Email, user.Email),                                                                new Claim(ClaimTypes.Gender, user.Gender),                                                                new Claim(ClaimTypes.GivenName, user.FirstName),                                                                new Claim(ClaimTypes.Surname, user.LastName)                                                             });        return principal;    }}

You would then hook it up in ConfigureServices just after calling AddIdentity like this...

         services.AddIdentity<IUser, IApplicationRole>()         .AddDefaultTokenProviders();        // Add Custom Claims processor        services.AddScoped<IUserClaimsPrincipalFactory<IUser>, CustomClaimsPrincipalFactory>();

Here is a very good article on the subject...

https://www.codeguru.com/csharp/csharp/cs_misc/security/asp.net-core-and-claim-based-security.html

Then in the view page

@(((ClaimsIdentity)User.Identity).FindFirstValue("firstName"))

It will show the authenticated user firstName.

and import the following packages at the top of the page

@using Microsoft.AspNet.Identity@using System.Security.Claims;