已有打开的与此命令相关联的 DataReader，必须首先将它关闭。

        public IList<RoadShow> SearchAll()
        {
            IList<RoadShow> list = new List<RoadShow>();
            using (SqlDataReader dr = DBHelper.ExecuteReader("select * from RoadShow"))
            {
                while (dr.Read())
                {
                    RoadShow road = new RoadShow();
                    road.Id = int.Parse(dr["ID"].ToString());
                    road.Answer = bool.Parse(dr["Answer"].ToString());
                    road.Ask = bool.Parse(dr["Ask"].ToString());
                    road.IsAnswer = bool.Parse(dr["IsAnswer"].ToString());
                    road.Contents = dr["Contents"].ToString();
                    road.Ip = dr["Ip"].ToString();
                    road.Datetime = DateTime.Parse(dr["Datetime"].ToString());
                    road.ReplyId = int.Parse(dr["ReplyId"].ToString());
                    RolesDAL dal = new RolesDAL();
                    int rolesid = int.Parse(dr["Roles"].ToString());
                    road.Roles = dal.SearchRolesById(rolesid);
                    list.Add(road);
                }
                dr.Close();
            }            
            DBHelper.Ocon.Close();
            return list;
        }

        public Roles SearchRolesById(int id)
        {
            Roles roles = new Roles();
            SqlParameter par = new SqlParameter("@ID", id);
            using (SqlDataReader dr = DBHelper.ExecuteReader("select * from roles where ID = @ID", par))
            {
                if (dr.Read())
                {
                    roles.Id = (int)dr["ID"];
                    roles.Code = dr["Code"].ToString();
                    roles.Role = dr["Role"].ToString();
                    roles.RoleId = (int)dr["RoleId"];
                }
                dr.Close();
            }            
            DBHelper.Ocon.Close();
            return roles;
        }

        public static SqlConnection Ocon
        {
            get
            {
                string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                if (ocon == null)
                {
                    ocon = new SqlConnection(connectionString);
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Closed)
                {
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Broken)
                {
                    ocon.Close();
                    ocon.Open();
                }
                return ocon;
            }
        }

        /// <summary>
        /// 执行结果集(非外键表)
        /// </summary>
        /// <param name="safeSql">sql语句</param>
        /// <returns>集合</returns>
        public static SqlDataReader ExecuteReader(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, Ocon);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        /// <summary>
        /// 执行结果集(非外键表)
        /// </summary>
        /// <param name="sql">sql语句</param>
        /// <param name="value">sql语句单个参数(对应表中字段)</param>
        /// <returns>集合</returns>
        public static SqlDataReader ExecuteReader(string sql, SqlParameter value)
        {
            SqlCommand cmd = new SqlCommand(sql, Ocon);
            cmd.Parameters.Add(value);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }

private static SqlConnection ocon = null;
        private static string str = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        public static SqlConnection Ocon

private static SqlConnection ocon = null;
        private static string str = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        public static SqlConnection Ocon
        {
            get
            {
                string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                if (ocon == null)
                {
                    ocon = new SqlConnection(connectionString);
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Closed)
                {
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Broken)
                {
                    ocon.Close();
                    ocon.Open();
                }
                return ocon;
            }

        public static SqlDataReader ExecuteReader(string safeSql)
        {
            SqlCommand cmd = new SqlCommand(safeSql, GetConnection());
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
        public static SqlDataReader ExecuteReader(string sql, SqlParameter value)
        {
            SqlCommand cmd = new SqlCommand(sql, GetConnection());
            cmd.Parameters.Add(value);
            SqlDataReader reader = cmd.ExecuteReader();
            return reader;
        }
public SqlConnection GetConnection()
{
                string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
                SqlConncection ocon；
                if (ocon == null)
                {
                    ocon = new SqlConnection(connectionString);
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Closed)
                {
                    ocon.Open();
                }
                else if (ocon.State == ConnectionState.Broken)
                {
                    ocon.Close();
                    ocon.Open();
                }
                return ocon;
}