Two questions about MVC, and Identity

Question

I am very new to identity and MVC, I am trying to create an MVC app as one of my first projects.

I have been able to follow a few tutorials and have successfully added additional properties to my ApplicationUser : IdentityUser class

public class ApplicationUser
    : IdentityUser<string, ApplicationUserLogin,
    ApplicationUserRole, ApplicationUserClaim>
{
    [Required]
    [Display(Name = "UserName")]
    [StringLength(50)]
    public string Handle { get; set; }

    [StringLength(100, ErrorMessage = "Your {0} can be at most {1} characters long.")]
    [Display(Name = "First Name")]
    public string FirstName { get; set; }

    [StringLength(100, ErrorMessage = "Your {0} can be at most {1} characters long.")]
    [Display(Name = "Last Name")]
    public string LastName { get; set; }

    [Required]
    [Display(Name = "User Creation Date")]
    public DateTime UserCreationDate { get; set; }

    public ApplicationUser()
    {
        this.Id = Guid.NewGuid().ToString();

        // Add any custom User properties/code here
    }

My questions are:

1. I see where Email is set to require a unique Email in App_Start.IdentityConfig.cs, Is there a way to set it up to require a unique custom property like Handle?

       var manager = new ApplicationUserManager(new UserStore<ApplicationUser, ApplicationRole, string, ApplicationUserLogin, ApplicationUserRole, ApplicationUserClaim>(context.Get<ApplicationDbContext>()));
       // Configure validation logic for usernames
       manager.UserValidator = new UserValidator<ApplicationUser>(manager)
       {
           AllowOnlyAlphanumericUserNames = false,
           RequireUniqueEmail = true
       };
   

2. In the Partial View of Views.Shared._LoginPartial.cshtml it shows the UserName/Email of the person logging into the application using User.Identity.GetUserName() is there a way to reference one of my custom properties there instead such as FirstName, or Handle?

   @using Microsoft.AspNet.Identity
   
   @if (Request.IsAuthenticated)
   {
       using (Html.BeginForm("LogOff", "Account", FormMethod.Post, new { id = "logoutForm", @class = "navbar-right" }))
       {
       @Html.AntiForgeryToken()
   
       <ul class="nav navbar-nav navbar-right">
           <li>
               @Html.ActionLink("Hello " + User.Identity.GetUserName() + "!", "Index", "Manage", routeValues: null, htmlAttributes: new { title = "Manage" })
           </li>
           <li><a href="javascript:document.getElementById('logoutForm').submit()">Log off</a></li>
       </ul>
       }
   }
   else
   {
       <ul class="nav navbar-nav navbar-right">
           <li>@Html.ActionLink("Register", "Register", "Account", routeValues: null, htmlAttributes: new { id = "registerLink" })</li>
           <li>@Html.ActionLink("Log in", "Login", "Account", routeValues: null, htmlAttributes: new { id = "loginLink" })</li>
       </ul>
   }
   

Answer 1

Implementing a custom UserValidator has already been covered here: How can customize Asp.net Identity 2 username already taken validation message?

Rather than hitting the database for every page request to display the handle, add a claim during signin.

Define your own claim:

public static class CustomClaimTypes
{
    public const string Handle = "http://schemas.xmlsoap.org/ws/2014/03/mystuff/claims/handle";
}

During signin, set the claim:

private async Task SignInAsync(ApplicationUser user, bool isPersistent, string password = null)
{
    AuthenticationManager.SignOut(DefaultAuthenticationTypes.ExternalCookie);

    var identity = await UserManager.CreateIdentityAsync(user, DefaultAuthenticationTypes.ApplicationCookie);

    //Get the handle and add the claim to the identity.
    var handle = GetTheHandle();
    identity.AddClaim(new Claim(CustomClaimTypes.Handle, handle);

    AuthenticationManager.SignIn(new AuthenticationProperties() { IsPersistent = isPersistent }, identity);
}

Then, via an extension method you can read it out the same way as GetUserName():

public static class IdentityExtensions
{
    public static string GetHandle(this IIdentity identity)
    {
        if (identity == null)
            return null;

        return (identity as ClaimsIdentity).FirstOrNull(CustomClaimTypes.Handle);
    }

    internal static string FirstOrNull(this ClaimsIdentity identity, string claimType)
    {
        var val = identity.FindFirst(claimType);

        return val == null ? null : val.Value;
    }
}

Finally, in your view:

@User.Identity.GetHandle()