How can I change UserManager logic so that user must exist in database before they register - asp.net-mvc-5

Question

I am customizing the MVC5 registration process so that when users are registering they must enter two custom fields 'MyNewField1' and 'MyNewField2' which will be then checked against the user context to ensure if they exist in which case the registration can succeed by updating that current user.
public async Task<ActionResult> CustomRegister(CustomRegisterViewModel model)
{
if (ModelState.IsValid)
{
var context = new ApplicationDbContext();
ApplicationUser user = context.Users.Where(a => a.MyNewField1== model.MyNewField1& a.MyNewField2== a.MyNewField2).SingleOrDefault();
if(user != null)
{
var emailCheck = await UserManager.FindByNameAsync(model.Email);
if (emailCheck == null)
{
//We have found a user and email address has not been already assigned to another
//assign the email entered for this user in place of the username and email place
//holders and update the user before saving to the database
user.UserName = model.Email;
user.Email = model.Email;
var hasher = new PasswordHasher();
user.PasswordHash = hasher.HashPassword(model.Password);
context.SaveChanges();
var code = await UserManager.GenerateEmailConfirmationTokenAsync(user.Id);
var callbackUrl = Url.Action("ConfirmEmail", "Account", new { userId = user.Id, code = code }, protocol: Request.Url.Scheme);
await UserManager.SendEmailAsync(user.Id, "Budget Energy Email Verification", "Please confirm your account by clicking this link: link");
ViewBag.Link = callbackUrl;
ViewBag.Message = "Check your email and confirm your account, you must be confirmed before you can log in.";
return View("Info");
}
else
{
//This email address is already assigned to a user
return View(model);
}
}
else
{
//No user exists with these details so redisplay form
return View(model);
}
}
}
This method is passing off successfully and I am being informed that an email has been sent however when I click on this email link I am taken to an error page with the error being Invalid Token. Because I have changed the logic here do I have to create a token in a different manner?

Answer 1

I was able to solve this as follows:
[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public async Task<ActionResult> BillpayRegister(BillpayRegisterViewModel model)
{
if (ModelState.IsValid)
{
var context = new ApplicationDbContext();
ApplicationUser customer = context.Users.Where(a => a.MyNewField1 == model.MyNewField1 & a.MyNewField2 == model.MyNewField2).SingleOrDefault();
if(customer != null)
{
var emailCheck = await UserManager.FindByNameAsync(model.Email);
if (emailCheck == null)
{
//We have found a user and email address has not been already assigned to another
//assign the email entered for this user in place of the username and email place
//holders and update the user before saving to the database
var user = UserManager.FindById(customer.Id);
user.UserName = model.Email;
UserManager.SetEmail(user.Id, model.Email);
string hashedNewPassword = UserManager.PasswordHasher.HashPassword(model.Password);
user.PasswordHash = hashedNewPassword;
var result = UserManager.Update(user);
if (result.Succeeded)
{
var code = await UserManager.GenerateEmailConfirmationTokenAsync(user.Id);
var callbackUrl = Url.Action("ConfirmEmail", "Account", new { userId = user.Id, code = code }, protocol: Request.Url.Scheme);
await UserManager.SendEmailAsync(user.Id, "Email Verification", "Please confirm your account by clicking this link: link");
ViewBag.Link = callbackUrl;
ViewBag.Message = "Check your email and confirm your account, you must be confirmed before you can log in.";
return View("Info");
}
}
else
{
//This email address is already assigned to a user
return View(model);
}
}
else
{
//No user exists with these details so redisplay form
return View(model);
}
}
// If we got this far, something failed, redisplay form
return View(model);
}