RegistrationPage.cs

public class RegistrationPage
{
    private readonly IWebDriver driver;
    private readonly string url = @"http://www.automatetheplanet.com/register";

    public RegistrationPage(IWebDriver browser)
    {
        this.driver = browser;
        PageFactory.InitElements(browser, this);
    }

    [FindsBy(How = How.Id, Using = "emailId")]
    public IWebElement Email { get; set; }

    [FindsBy(How = How.Id, Using = "passId")]
    public IWebElement Pass { get; set; }

    [FindsBy(How = How.Id, Using = "userNameId")]
    public IWebElement UserName { get; set; }

    [FindsBy(How = How.Id, Using = "registerBtnId")]
    public IWebElement RegisterButton { get; set; }

    public User RegisterUser(string email = null, string password = null, string userName = null)
    {
        var user = new User();
        this.driver.Navigate().GoToUrl(this.url);
        if (string.IsNullOrEmpty(email))
        {
            email = UniqueEmailGenerator.BuildUniqueEmailTimestamp();
        }
        user.Email = email;
        this.Email.SendKeys(email);
        if (string.IsNullOrEmpty(password))
        {
            password = TimestampBuilder.GenerateUniqueText();
        }
        user.Pass = password;
        this.Pass.SendKeys(password);
        if (string.IsNullOrEmpty(userName))
        {
            userName = TimestampBuilder.GenerateUniqueText();
        }
        user.UserName = userName;
        this.UserName.SendKeys(userName);
        this.RegisterButton.Click();
        return user;
    }
}