如何使用signalR通知数据库更改

我刚刚开始使用SignalR，想尝试一下实时通知。目标是保持在网页上显示更新的消息。有一个数据库表DummyData，它有一个列Message。该表只有一条记录——Hello当页面加载时，显示"Hello"

然后在sql server 2012中手动运行该命令

update DummyData set Message='hello world'，但网页上没有更新消息

aspx:

<script>
    $(function () {
        var notify = $.connection.notificationsHub;
        $.connection.hub.start().done(function () {
            notify.server.notifyAllClients();
        });
        notify.client.displayNotification = function (msg) {               
            $("#newData").html(msg);
        };
        notify.client.stopClient = function () {
            $.connection.hub.stop();
        };
    });
</script>
 <span id="newData"></span>

aspx.cs:

public string SendNotifications()
    {
      string message = string.Empty;
      using (SqlConnection connection = new SqlConnection(conStr))
       {
        string query = "SELECT [Message] FROM [dbo].[DummyData]";
        SqlCommand command = new SqlCommand(query, connection)
        command.Notification = null;
        SqlDependency dependency = new SqlDependency(command);
                dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
        connection.Open();
        SqlDataReader reader = command.ExecuteReader();
        if (reader.HasRows)
        {
         reader.Read();
         message = reader[0].ToString();
        }
       }            
        return message;
    }
    private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
    {
        if (e.Type == SqlNotificationType.Change)
        {
            SendNotifications();
        }            
    }

NotificationsHub.cs

public class NotificationsHub : Hub
{
 Messages obj = new Messages();
 public void NotifyAllClients(string msg)
  {
   IHubContext context = GlobalHost.ConnectionManager.GetHubContext<NotificationsHub>();
   context.Clients.All.displayNotification(msg);
  }
 public override System.Threading.Tasks.Task OnConnected()
  {
   NotifyAllClients();
   return base.OnConnected();
  }
 public override System.Threading.Tasks.Task OnDisconnected(bool stopCalled)
 {
  NotifyAllClients();
  return base.OnDisconnected(stopCalled);
 }
}

global.asax:

protected void Application_Start(object sender, EventArgs e)
        {
            SqlDependency.Start(Constr);
        }

当我运行tsql update命令时，断点首先在dependency_OnChange处命中，我可以看到从SendNotification返回的新更新的文本。但它并没有反映在书页上。

public override OnConnected()
{
  // Increase the active user count in the db 
  IHubContext context = GlobalHost.ConnectionManager.GetHubContext<ServerHub>();
  Clients.All.broadcastCount(DB.GetCount());
  return base.OnConnected();
}
public override OnDisconnected() 
{
    //Decrease the connected user count in the db
  IHubContext context = GlobalHost.ConnectionManager.GetHubContext<ServerHub>();
  Clients.All.broadcastCount(DB.GetCount());
  return base.OnDisconnected();
}