int i = 0; DataTable dt = new DataTable(); //实例化DataTable dt = mycon.myDataTable(sql); //执行SQL语句并返回DataTable i = dt.Rows.Count; if (i > 0) { if (yhma == querenmima.Text.Trim()) { sql2 = String.Format("update users set UserPassword='{0}' where userdz='{1}'", yhma, ygxm); mycon.myExecuteNonQuery(sql2);