How to pass Area in Url.Action?

You can use this Url.Action("actionName", "controllerName", new { Area = "areaName" });

Also don’t forget to add the namespace of the controller to avoid a conflict between the admin area controller names and the site controller names.

Something like this

 public override void RegisterArea(AreaRegistrationContext context)
        {
            context.MapRoute(
                "Admin_default",
                "Admin/{controller}/{action}/{id}",
                new { action = "Index", id = UrlParameter.Optional },
                  new[] { "Site.Mvc.Areas.Admin.Controllers" }
            );
        }