2qcq0V0F

1public class RegisterViewModel
2{
3    [Required]
4    [EmailAddress]
5    [Remote(action: nameof(AccountController.IsEmailNotInUseAndDomainValid), controller: "Account")]
6    [ValidEmailDomain("gmail.com", ErrorMessage = "Email domain must be 'gmail.com'")]
7    public string Email { get; set; }
8
9    // ...
10}
11
12public class AccountController : Controller
13{
14	// ...
15
16	[AcceptVerbs("Get", "Post")]
17    [AllowAnonymous]
18    public async Task<IActionResult> IsEmailNotInUseAndDomainValid(string email)
19    {
20        var isEmailInUse = await IsEmailNotInUseAsync(email);
21        if (isEmailInUse.Value is bool notInUse && notInUse != true || !(isEmailInUse.Value is bool))
22            return isEmailInUse;
23
24        var isDomainValid = IsDomainValid(email);
25        if (isDomainValid.Value is bool valid && valid != true || !(isDomainValid.Value is bool))
26            return isDomainValid;
27
28        return Json(true);
29    }
30
31    public async Task<JsonResult> IsEmailNotInUseAsync(string email)
32    {
33        var user = await _userManager.FindByEmailAsync(email);
34        return user == null 
35            ? Json(true) 
36            : Json($"Email {email} is already in use.");
37    }
38
39    public JsonResult IsDomainValid(string email)
40    {
41        var validEmailDomainAttribute = typeof(RegisterViewModel).GetTypeInfo()?
42            .GetProperty(nameof(RegisterViewModel.Email))?.GetCustomAttribute<ValidEmailDomainAttribute>();
43        return validEmailDomainAttribute?.IsValid(email) switch
44        {
45            true => Json(true),
46            false => Json(validEmailDomainAttribute.ErrorMessage),
47            _ => throw new NullReferenceException()
48        };
49    }
50
51	// ...
52}