The datatable bound to the grid, assume the datatable is dtGrid. Save that in a ViewState/Session
Below I have provided a sample code. I hope this gives you an idea to build on...
This code will add empty row...
OnAddNew_Click()
{
dtGrid=(DataTable)ViewState["dt"];
DataRow dr = dtGrid.NewRow();
dr[0]=""
dr[1]=""
dr[2]=""
dr[3]=""
dr[4]=""
dtGrid.Rows.Add(dr);
gridView.DataSource=dtGrid;
gridView.DataBind();
}
Hope this helps