Question

I am comparing a username using a custom validation. I am checking if it’s the same as the old value or if it passes the regex it is acceptable but if it is not then throw an error. How do i get the UserID from the viewmodel if possible?

    [EmailValidation]
    public string Username{ get; set; }
    public int UserID { get; set; }



public class EmailValidationAttribute : ValidationAttribute
    {
         protected override ValidationResult IsValid(object value, ValidationContext validationContext)
         {

             User user= User.getUserByID(UserID); //How to get UserID?
             string username= value.ToString();
             if (user.Username== username || IsValid(username))
                {
                    return ValidationResult.Success;
                }
                else
                {
                    return new ValidationResult("Error");
                }

            }

Answer 1

You can get UserID from ObjectInstance of ValidationContext. In your case it will be instance of your User class.

public class EmailValidationAttribute : ValidationAttribute
{
     protected override ValidationResult IsValid(object value, ValidationContext validationContext)
     {
         UserDto dto = (UserDto)validationContext.ObjectInstance;
         User user= User.getUserByID(dto.UserID);
         string username = value.ToString();
         if (user.Username == username || IsValid(username))
         {
            return ValidationResult.Success;
         }
         else
         {
            return new ValidationResult("Error");
         }

    }
}

If you want something more universal you can add property that specify property name and use reflection to get the value.