in my webdatagrid 

in page load of server side

List<Supp> Details = new List<Supp>();
Details.Add(new Supp() { srno = 1, service_name = "--Select--", service_id = 0, country_name = "--Select--", country_id = 0, destination = "--Select--", curr_code = "--Select--", group_name = "--Select--", from_date = null, to_date = null, category = "", budget_cost = 0.00, superior_cost = 0.00, premium_cost = 0.00, other_service_cost = 0.00, star_rating = "", check_in_time = null, check_out_time = null, rooms = 0, facility = "", destination_id = 0, curr_id = 0, pricing_group_id = 0 }); // service_id = 0, country_id = 0, destination_id = 0, curr_id = 0, pricing_group_id = 0
Session.Add("MyList", Details);

i am maintaining this for blank row should be created. in new mode i have created client side event of cell existed edit mode on this i have 

var ID = Masters_Supplier_dtl.SrNo(count);
var values = [parseInt(ID.value), "--Select--", "--Select--", "--Select--", "--Select--", "--Select--", null, null, "", 0.0, 0.0, 0.0, 0.0,"", null, null, 0, "",0,0,0,0,0]; //null, null, "", 0.0, 0.0, 0.0, 0.0,
grid.get_rows().add(values);

by this grid rows increase by 1

but in edit mode it not works properly