解决"另一个 SqlParameterCollection 中已包含 SqlParameter"这个异常？？

下面只粘了部分代码
这个是我写的方法
   #region 查找所有用户
        public UserInfo[] GetAllUserInfo()
        {
             IList<UserInfo> iuser = new List<UserInfo>();
             try
             {
                 IDataReader reader = DBHelper.ExecuteReader("sp_UserInfo_SelectAll");
                 while (reader.Read())
                 {
                     UserInfo user = new UserInfo();
                     user.UserSeq = (int)reader["USER_SEQ"];
                     user.UserId = (string)reader["USER_ID"];
                     user.UserName = reader["USER_NAME"].ToString();
                     user.Password = reader["PASSWORD"].ToString();
                     user.Phone = reader["PHONE"].ToString();
                     user.Department = reader["DEPARTMENT"].ToString();
                     user.Email = reader["EMAIL"].ToString();
                     user.InitPwdStatus = reader["INIT_PWD_STATUS"].ToString();
                     user.DelStatus = reader["DEL_STATUS"].ToString();
                     iuser.Add(user);
                 }             }
             catch(Exception e)
             {
                 throw e;
             }
             finally
             {
                 DBHelper.CloseReader();
             }
             return iuser.ToArray();
        }
这个是我调用工场类里面的ExecuteReader方法
        public IDataReader ExecuteReader(CommandType commandType, string commandText)
        {
            Command = DBFactory.GetCommand(ProviderType);
            Command.Connection = Connection;
            PrepareCommand(Command, Connection, Transaction, commandType, commandText, Parameters);
            DataReader = Command.ExecuteReader();
            Command.Parameters.Clear();
            return DataReader;
        } 我在调用GetAllUserInfo()时有异常另一个 SqlParameterCollection 中已包含 SqlParameter"
Command.Parameters.Clear();应该是已经清理了，但是为什么还会有这样的异常？？？忘高手解决下，谢谢啦！！！！！