Why the exception "No Object Found on Server" is coming in LDAP ?

DirectoryEntry rootEntry = new DirectoryEntry("LDAP://NESTIT-283:389");


                 rootEntry.AuthenticationType = AuthenticationTypes.None; //Or whatever it need be
                 DirectorySearcher searcher = new DirectorySearcher(rootEntry);
                 string searchString = "(CN = EFTS-CA-TEST)";
                 var queryFormat = "(&(objectClass=user)(objectCategory=person)(|(SAMAccountName=*{0}*)(cn=*{0}*)(gn=*{0}*)(sn=*{0}*)(email=*{0}*)))";
                 //searcher.Filter = string.Format(queryFormat, searchString);

                 searcher.Filter = searchString;//Search how you want.  Google "LDAP Filter" for more.
                 foreach (SearchResult result in searcher.FindAll())
                 {
                     Console.WriteLine("account name: {0}", result.Properties["samaccountname"].Count > 0 ? result.Properties["samaccountname"][0] : string.Empty);
                     Console.WriteLine("common name: {0}", result.Properties["cn"].Count > 0 ? result.Properties["cn"][0] : string.Empty);
                 }