object reference not set to an instance object

i get error on high lighted code 

using Microsoft.Web.Administration;

ServerManager serverManager = new ServerManager();
            //get the site (e.g. default)
            Site site = serverManager.Sites.FirstOrDefault(s => s.Name == "ERP3");

            //Protocol hhtp, https....
           
            httpcontext.current.response.write(site.Bindings.ElementAt(0).EndPoint.Address);
                //Puerto
            httpcontext.current.response.write(site.Bindings.ElementAt(0).EndPoint.Port);

i get error on that high light 

object reference not set to an instance object