Assuming you are using the default routes:
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
"Default",
"{controller}/{action}/{id}",
new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);
}
If you need to specify the controller name try this (don't forget the last parameter - the html attributes which I am passing to null here):
<%: Html.ActionLink("Contacts", "Index", "Contacts", new { id = item.CompanyID }, null) %>
or without specifying the controller (using the current controller):
<%: Html.ActionLink("Contacts", "Index", new { id = item.CompanyID }) %>