ASP.NET Identity and Web API - Problem to register new user

Question

I have a Web API project and I’m using Identity to manage user accounts, my controller is like this:

public async Task<IHttpActionResult> Register([FromBody]RegisterDto model)
{
    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    try
    {
        var registerDomain = Mapper.Map<RegisterDto, Customer>(model);
        registerDomain.UserName = registerDomain.Email;
        _customerService.Insert(registerDomain);
        IdentityResult result = await UserManager.CreateAsync(registerDomain, model.Password);

        if (!result.Succeeded)
        {
            return GetErrorResult(result);
        }

        var code = await UserManager.GenerateEmailConfirmationTokenAsync(registerDomain.Id); 
        var callbackUrl = Url.Link("DefaultApi", new { controller = "Account", action = "ConfirmEmail", userId = registerDomain.Id, code = code });
        await UserManager.SendEmailAsync(registerDomain.Id, "Confirmação de conta", "Porfavor confirme a sua conta clicando nesse link: <a href=\"" + callbackUrl + "\">link</a>");
    }
    catch (Exception ex)
    {
        return BadRequest();
    }

    return Ok();
}

But the result of UserManager.CreateAsync is making the following mistake: Name cannot be null or empty.

Name is a property of Customer (Customer inherits from IdentityUser) and the string is being passed on correctly, including in RegisterDto the property is required, if it was null or empty it did not pass the ModelState.

I’ve searched the net and there are people with the same problem, but the solutions are not working, someone can give a tip?

The code of RegisterDto

public class RegisterDto
{
    public string Id { get; set; }

    [Required]
    public string Name { get; set; }

    [Required]
    public int Cpf { get; set; }

    [Required]
    public string Email { get; set; }

    [Required]
    [DataType(DataType.Password)]
    public string Password { get; set; }

    [Required]
    [DataType(DataType.Password)]
    [Compare("Password", ErrorMessage = "A senha e a confirmação da senha não são iguais.")]
    public string ConfirmPassword { get; set; }
}

Answer 1

This problem is not very easy to solve because the error message does not help much. Actually the source of the problem is here:

registerDomain.UserName = registerDomain.Email;

By default, the user entity validator does not accept characters like the @ and the . in UserName. This is why it is necessary to adjust the validator before accepting special characters for the user name:

UserManager.UserValidator = new UserValidator<TUser>(UserManager) { 
                                  AllowOnlyAlphanumericUserNames = false }