You cannot include the query string in the route. Try with a route like this:
routes.MapRoute("OpenCase", "ABC/ABC{stepNo}",
new { controller = "ABC1", action = "OpenCase" });
Then, on your controller add a method like this:
public class ABC1 : Controller
{
public ActionResult OpenCase(string stepno, string key, string group)
{
// do stuff here
return View();
}
}
ASP.NET MVC will automatically map the query string parameters to the parameters in the method in the controller.