public void Add(ExamClass model)
 {
     try
     {
         /* 操作本地数据 */
         LocalData.Insert(0, model);
     }
     catch
     {
         Console.WriteLine("Error of adding data");
         return;
     }
 }
 public void Edit(int id, ExamClass model)
 {
     try
     {
         /* 操作本地数据 */
         int ind = LocalData.FindIndex(item => item.Id == id);
         LocalData.RemoveAt(ind);
         LocalData.Insert(ind, model);
     }
     catch
     {
         Console.WriteLine("Error of editing data");
         return;
     }
 }
        public int Edit(int id, ExamClass model)
        {
            try
            {
                /* 操作本地数据 */
                int ind = LocalData.FindIndex(item => item.Id == id);
                if (ind >= 0 && ind < LocalData.Count)
                {
                    LocalData.RemoveAt(ind);
                    LocalData.Insert(index, model);
                }

                return(UploadToSQL());
                ///* 数据库同步操作 */
                //using (var connect = new NpgsqlConnection(connectSql))
                //{
                //    connect.Open();
                //    string updateSql = string.Format("UPDATE {0} SET Id=@param0, ClassNo=@param1, InstituteStudents=@param2, NumberStudents=@param3, " +
                //                                    "InstituteProctors=@param4, NumberProctors=@param5 WHERE Id = {1};", tableName, id);
                //    using (var updateCmd = new NpgsqlCommand(updateSql, connect))
                //    {
                //        updateCmd.Parameters.AddWithValue("param0", NpgsqlDbType.Integer, model.Id);
                //        updateCmd.Parameters.AddWithValue("param1", NpgsqlDbType.Text, model.ClassNo);
                //        updateCmd.Parameters.AddWithValue("param2", NpgsqlDbType.Text, model.InstituteStudents);
                //        updateCmd.Parameters.AddWithValue("param3", NpgsqlDbType.Integer, model.NumberStudents);
                //        updateCmd.Parameters.AddWithValue("param4", NpgsqlDbType.Text, model.InstituteProctors);
                //        updateCmd.Parameters.AddWithValue("param5", NpgsqlDbType.Integer, model.NumberProctors);

                //        int count = updateCmd.ExecuteNonQuery();
                //        Console.WriteLine("Succeed to edit data of 'ClassNo:{0}' to Table: {1}.{2} ", model.ClassNo, sqlName, tableName);
                //        return count;
                //    }
                //}
            }
            catch
            {
                Console.WriteLine("Error of editing data to {0}.{1}", sqlName, tableName);
                return(-1);
            }
        }