class DBHelper    {        public static string connstr = "server=;database;uid=;pwd=;";        public int ExecuteNoQuery(string sql,params SqlParameter[] param)        {            using (SqlConnection conn = new SqlConnection(connstr))            {                conn.Open();                using(SqlCommand cmd=conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(param);                    return cmd.ExecuteNonQuery();                }            }        }        public Object ExecuteScalar(string sql, params SqlParameter[] param)        {            using (SqlConnection conn = new SqlConnection(connstr))            {                conn.Open();                using (SqlCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(param);                    return cmd.ExecuteScalar();                }            }        }        public DataTable ExecuteTable(string sql,params SqlParameter[] param)        {            using (SqlConnection conn = new SqlConnection(connstr))            {                conn.Open();                using (SqlCommand cmd = conn.CreateCommand())                {                    cmd.CommandText = sql;                    cmd.Parameters.AddRange(param);                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);                    DataTable dt = new DataTable();                    adapter.Fill(dt);                    return dt;                }            }        }        public void FillListView(ListView lv,DataTable dt,params string[] headers)        {            lv.Clear();            lv.BeginUpdate();            for (int i = 0; i < headers.Length;i++ )            {                lv.Columns.Add(headers[i],lv.Width/headers.Length-2);            }            for (int i = 0; i < dt.Rows.Count;i++ )            {                ListViewItem item = new ListViewItem();                item.Text = dt.Rows[i][0] + "";                for(int j=1;j