How to check phone number is unique in AspNetUsers table when using ASP.NET Web Api

Question

I have created an Asp.Net Web Api project and used Individual user accounts. When I am adding users to the table the default system automatically checks if the email address supplied already exists in the table, if so a bad request is thrown otherwise the user can be submitted.

How can I also check if the Phone Number is unique and hasn't already been submitted to the table?

// POST api/Account/Register
        [AllowAnonymous]
        [Route("Register")]
        public async Task<IHttpActionResult> Register(RegisterBindingModel model)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            **using (ApplicationDbContext db = new ApplicationDbContext())
            {
                var foundPhoneNumber = await db.Users.FirstOrDefaultAsync(x => x.PhoneNumber.Equals(model.PhoneNumber));

                if (foundPhoneNumber != null)
                {
                    return BadRequest("Phone number already exists");
                }
            }**

            var user = new ApplicationUser()
            {
                UserName = model.Email,
                Email = model.Email,
                PhoneNumber = model.PhoneNumber,
                FirstName = model.FirstName,
                LastName = model.LastName,
                MemberNumber = model.MemberNumber,
                CarReg = model.CarReg
            };

            IdentityResult result = await UserManager.CreateAsync(user, model.Password);

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

            return Ok();
        }

I have queried the database to check if there is a Phone Number with the same number. This works, but is there a better way to do this?

Answer 1

Modify your ApplicationUser call and add the following attributes.

public class ApplicationUser : IdentityUser
{
    [MaxLength(17)]
    [IsUnique]
    public string PhoneNumber { get; set; }
}

Answer 2

You can override ValidateEntity method in ApplicationUserDbContext class, it will trigger on SaveChanges method.

protected override DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry, IDictionary<object, object> items)
        {
            if (entityEntry != null && entityEntry.State == EntityState.Added)
            {
                var errors = new List<DbValidationError>();
                ////User Validation
                if (entityEntry.Entity is ApplicationUser user)
                {
                    if (this.Users.Any(u => string.Equals(u.PhoneNumber, user.PhoneNumber)))
                    {
                        errors.Add(new DbValidationError("User",
                          string.Format($"Phonenumber {user.PhoneNumber} is already taken")));
                    }
                }

                if (errors.Any())
                {
                    return new DbEntityValidationResult(entityEntry, errors);
                }
            }
            return new DbEntityValidationResult(entityEntry, new List<DbValidationError>());
        }

Answer 3

Validation can be added via a custom ValidationAttribute that you add to the PhoneNumber property on you model. Here is a simple example:

   [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
   public class NotABananaAttribute : ValidationAttribute
   {
    public override bool IsValid(object value)
    {
        var inputValue = value as string;
        var isValid = true;

        if (!string.IsNullOrEmpty(inputValue))
        {
            isValid = inputValue.ToUpperInvariant() != "BANANA";
        }

        return isValid;
    }
   }

And its used liked this...

public class Model
{
    [NotABanana(ErrorMessage = "Bananas are not allowed.")]
    public string FavoriteFruit { get; set; }
}

Example sourced from: https://riptutorial.com/csharp/example/18486/creating-a-custom-validation-attribute