I'm discovering about NHtmlUnit to build an application web. But when I try it with auto login to yahoo mail. But after I run code. I refresh the login page of Yahoo so nothing changed. Not logged.

Code:

```
        NHtmlUnit.WebClient driver = new NHtmlUnit.WebClient();

        driver.Options.JavaScriptEnabled = true;
        driver.Options.ThrowExceptionOnScriptError = false;
        driver.Options.ActiveXNative = true;
        driver.Options.CssEnabled = true;

        HtmlPage page = driver.GetHtmlPage("https://login.yahoo.com/config/login?");

        HtmlForm form = page.GetFormByName("login_form");
        HtmlTextInput user = (HtmlTextInput)form.GetInputByName("login");
        HtmlPasswordInput pass = (HtmlPasswordInput)form.GetInputByName("passwd");

        user.SetValueAttribute("my account");
        pass.SetValueAttribute("my pass");

        HtmlSubmitInput submitButton = (HtmlSubmitInput)page.GetElementByName(".save");

        HtmlPage nextpage = (HtmlPage)submitButton.Click();

```

Please help me why. I write it on .NET MVC 4 C#. Thank you very much.