ImproperUtilization.cs

public void Create(User user)
  {    
      if(string.IsNullOrWhiteSpace(user.Email))
        throw new InvalidEmailException();
      
      if(!new Regex("^[A-Za-z]\w{6,}[A-Za-z]$").IsMatch(user.Password))
        throw new InvalidPasswordException();
    
      if(string.IsNullOrWhiteSpace(user.FirstName) || string.IsNullOrWhiteSpace(user.LastName))
        throw new InvalidNameException();
      
      var repo = new UserRepository();
      repo.Create(new UserEntity{
        Email = user.Email;
        Password = user.Password;
        FirstName = user.FirstName;
        LastName = user.LastName;
      });
  }