How to make dynamic menu based on role in nested master page asp.net mvc 4?

Question 1

First of all, you don't want to do this logic in a master page. You want to create a partial view that will build the menu based on the model information returned by a child action in some controller. For example:

You should move this logic into some controller that is in charge of building navigation. Inside of this controller you should declare a child action that returns the information that you need.

If you plan to store URL and Description in a database, you might as well store access privileges in a table as well. That way you can pass user's group or user name and retrieve a collection of URL to which that user has access. After that you could use a code similar to the one below.

For example:

public class NavigationController : Controller
{
    [ChildActionOnly]
    public PartialViewResult GetMenuForUser()
    {
        var model = _securityLayer.GetUrlForUser(HttpContext.User.Identity.Name);

        return PartialView("_UserMenu", model);
    }
}

Your _UserMenu.cshtml could be like:

@model IEnumerable<SomeCollection>

@foreach(var url in Model) {
    <li><a class="ajax-link" href="@url.Url">@url.Description</a></li>
}

THen in your master page, where you want to use the menu you would call:

<div class="well nav-collapse sidebar-nav">
    <ul class="nav nav-tabs nav-stacked main-menu">
        <li class="nav-header hidden-tablet">MAIN MENU</li>
        @{ Html.RenderAction("GetMenuForUser", "Navigation"); }
    </ul>
</div>

This should give you an idea how to proceed regardless of whether you store user access rights in a database.

UPDATE: Sorry, I realized later that you are using ASPX View Engine and not Razor. You will need to convert to ASPX View Engine my markup.

Question 2

Try creating a controller where you use identity to get an IList of the current user's roles then convert that list into a string separated with commas then store that in a viewbag or in tempdata depending on your preference then in your layout use the Viewbag data to display items basing on what role is found in there. This is the controller

        [Authorize]
    public ActionResult Index()
    {
        if (User.Identity.IsAuthenticated)
        {
            var user = User.Identity;
            ViewBag.Name = user.Name;
            ViewBag.DisplayMenu = UserRole();
            return View();
        }
        else
        {
            ViewBag.Name = "Not Logged in";
        }
        return View();
    }
    public string UserRole()
    {
        string urole = "non";
        if (User.Identity.IsAuthenticated)
        {
            var user = User.Identity;
            ApplicationDbContext context = new ApplicationDbContext();
            var UserManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(context));
            var s = UserManager.GetRoles(user.GetUserId());
            urole = String.Join(",", s.ToArray());
        }
        return urole;
    }