C# WCF服务中的BeginExecuteReader错误

我正在尝试在WCF服务中异步连接到数据库。但尽管在连接字符串中设置了“Asynchronous Processing=true”，我还是得到了

System.InvalidOperationException

带有消息

BeginExecuteReader:
连接属性尚未初始化。

我用来连接数据库的代码是：

public void Connect()
{
   using (SqlConnection conn = new SqlConnection("Data Source=User12-PC; Initial Catalog = BMS;  User Id=sa; Password = pass; Asynchronous Processing=true"))
   {
      SqlCommand command = new SqlCommand();
      command.CommandText = "Select l.currvalue from" +
                            " advt_ctrl_pts as p inner join advt_log_in_ctrl_pts l" +
                            " on p.registerid = l.regid and p.ddcid = l.ddcid" +
                            " where p.pointid = 5156102" +
                            " order by datetime";

      command.CommandType = CommandType.Text;

      conn.Open();
      IAsyncResult result = command.BeginExecuteReader(); //This part is returning exception
      if (result.IsCompleted)
      {
         timer = new Timer(new TimerCallback(onTimerTick), command.EndExecuteReader(result), 5000, 5000);
      }
   }
}

---

有人能告诉我我做错了什么吗？

您没有将连接分配给命令：

SqlCommand command = new SqlCommand();
command.Connection = conn;