What is sparse array?

http://en.wikipedia.org/wiki/Sparse_array
a sparse array is an array in which most of the elements have the same value (known as the default value—usually 0 or null).

How to render an action without layout in ASP.NET MVC?

    public class HomeController : Controller
    {
        public string Create()
        {
     return "Hello";
 }
    } 

There are a couple of other ways:
http://stackoverflow.com/questions/5318385/mvc-3-how-to-render-a-view-without-its-layout-page
Change Layout default setting etc.
But return a string or json result, it is great way in some scenarios.