ASP.NET MVC 5 windows authentication

Question

 I want to get the user domain name, username, login and password from Active Directory in my organization intranet.

Here is my web config file:


<system.web>
    <authentication mode="Windows"></authentication>
    <compilation debug="true" targetFramework="4.5" />
    <httpRuntime targetFramework="4.5" />
  </system.web>


HERE IS MY INDEX ACTION
public ActionResult Index()
        {
            var requestContext = new RequestContext();      
    string ntLogin = requestContext.HttpContext.User.Identity.Name


}

HERE IS THE ERROR I GET:

Object reference not set to an instance of an object.

What is it that I'm doing wrong. I want to get the user login and password from Active Directory in my organization intranet. What do I need to do next. Please help out.

Thanks