Add Custom User Data To Identity Core Register Form In ASP.NET Core 3.0

using System.Threading.Tasks;
using CustomUserData_Demo.Models;
using CustomUserData_Demo.ViewModel;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;

namespace CustomUserData_Demo.Controllers
{
    public class AccountController : Controller
    {
        private readonly UserManager<ApplicationUser> userManager;
        private readonly SignInManager<ApplicationUser> signInManager;
        
        public AccountController(UserManager<ApplicationUser> userManager,
                                  SignInManager<ApplicationUser> signInManager)
        {
            this.userManager = userManager;
            this.signInManager = signInManager;
        }
        
        public IActionResult Register()
        {
            return View();
        }
        
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Register(RegisterViewModel model)
        {
            if (ModelState.IsValid)
            {
                var user = new ApplicationUser
                {
                    FirstName = model.FirstName,
                    LastName = model.LastName,
                    PhoneNumber = model.PhoneNumber,
                    UserName = model.Email,
                    Email = model.Email,
                };
                
                var result = await userManager.CreateAsync(user, model.Password);
                
                if (result.Succeeded)
                {
                    await signInManager.SignInAsync(user, isPersistent: false);
                    return RedirectToAction("Index", "Home");
                }
                
                foreach (var error in result.Errors)
                {
                    ModelState.AddModelError("", error.Description);
                }
            }
            
            return View();
        }
    }
}

Step 8. Now right-click on the register action method and “Add View” with the default name Register to click on “Add”. It will be added under the views folder; account folder with Register.cshtml.

@model CustomUserData_Demo.ViewModel.RegisterViewModel

@{
    ViewData["Title"] = "Register";
}

<p class="row">
    <p class="col-md-8 mx-auto">
        <p class="card">
            <p class="card-header bg-primary text-white">
                <h5 class="text-uppercase text-center">User Registration Form</h5>
            </p>
            <p class="card-body">
                <form asp-action="Register">
                    <p class="row">
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="FirstName"></label>
                                <input asp-for="FirstName" class="form-control" />
                                <span asp-validation-for="FirstName" class="text-danger"></span>
                            </p>
                        </p>
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="LastName"></label>
                                <input asp-for="LastName" class="form-control" />
                                <span asp-validation-for="LastName" class="text-danger"></span>
                            </p>
                        </p>
                    </p>
                    <p class="row">
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="PhoneNumber"></label>
                                <input asp-for="PhoneNumber" class="form-control" />
                                <span asp-validation-for="PhoneNumber" class="text-danger"></span>
                            </p>
                        </p>
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="Email"></label>
                                <input asp-for="Email" class="form-control" />
                                <span asp-validation-for="Email" class="text-danger"></span>
                            </p>
                        </p>
                    </p>
                    <p class="row">
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="Password"></label>
                                <input asp-for="Password" class="form-control" />
                                <span asp-validation-for="Password" class="text-danger"></span>
                            </p>
                        </p>
                        <p class="col-md-6">
                            <p class="form-group">
                                <label asp-for="ConfirmPassword"></label>
                                <input asp-for="ConfirmPassword" class="form-control" />
                                <span asp-validation-for="ConfirmPassword" class="text-danger"></span>
                            </p>
                        </p>
                    </p>
                    <input type="submit" value="Register" class="btn btn-sm btn-primary text-uppercase rounded-0" />
                </form>
            </p>
        </p>
    </p>
</p>

Step 9. Now under the views folder find the shared folder open _LoginPartial.cshtml and modify it as below.

@using Microsoft.AspNetCore.Identity
@inject SignInManager<ApplicationUser> SignInManager
@inject UserManager<ApplicationUser> UserManager

<ul class="navbar-nav">
    @if (SignInManager.IsSignedIn(User))
    {

    }
    else
    {
        <li class="nav-item">
            <a class="nav-link" asp-controller="Account" asp-action="Register">Register</a>
        </li>
        <li class="nav-item">
            <a class="nav-link text-dark" asp-controller="Account" asp-action="Login">Login</a>
        </li>
    }
</ul>

Step 10. Now press ctrl+F5 and run your project.