两个注意点：

1、 sql 语句中用  count(*)

2. 转换行数时候用 Convert.ToInt32 ，不要强制转换

           try
            {
                OpenSql();  // 打开数据库

                string strCommond = string.Format("select count(*)  from {0} ", tableName);
                SQLiteCommand cmd = new SQLiteCommand(strCommond, m_dbConnection);
                int RowCount = Convert.ToInt32(cmd.ExecuteScalar());

                CloseSql();

                return RowCount;
            }
            catch (Exception ex)
            {
                throw ex;
            }