问SqlDependency与signalR没有一致地触发dependency_OnChange

EN

void Application_Start(object sender, EventArgs e)
{
    var queuename = "Q_Name";
    var sConn = ConfigurationManager.ConnectionStrings["singalR_ConnString"].ConnectionString;
    SqlDependency.Stop(sConn, queuename);
    SqlDependency.Start(sConn, queuename);
}

void Application_End(object sender, EventArgs e)
{  
    var queuename = "Q_Name";
    var sConn = ConfigurationManager.ConnectionStrings["singalR_ConnString"].ConnectionString;
    SqlDependency.Stop(sConn, queuename);
}

public void SendNotifications()
{
    //Identify Current User and Row No
    string CurrentUser = GetNTName();


    string message = string.Empty;
    string conStr = ConfigurationManager.ConnectionStrings["singalR_ConnString"].ConnectionString;

    using (SqlConnection connection = new SqlConnection(conStr))
    {
        string query = "SELECT [RowNo] FROM [dbo].[Test] WHERE [User] =  @User";
        string SERVICE_NAME = "Serv_Name";

        using (SqlCommand command = new SqlCommand(query, connection))
        {
            // Add parameters and set values.
            command.Parameters.Add("@User", SqlDbType.VarChar).Value = CurrentUser;
            //Need to clear notification object
            command.Notification = null;
            //Create new instance of sql dependency eventlistener (re-register for change events)
            SqlDependency dependency = new SqlDependency(command, "Service=" + SERVICE_NAME + ";", 0);
            //SqlDependency dependency = new SqlDependency(command);
            //Attach the change event handler which is responsible for calling the same SendNotifications() method once a change occurs.
            dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
            connection.Open();
            SqlDataReader reader = command.ExecuteReader();

            if (reader.HasRows)
            {
                reader.Read();
                message = reader[0].ToString();
            }
        }
    }
    //If query returns rows, read the first result and pass that to hub method - NotifyAllClients.
    NotificationsHub nHub = new NotificationsHub();
    nHub.NotifyAllClients(message);
}


private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{            
    //Check type to make sure a data change is occurring
    if (e.Type == SqlNotificationType.Change)
    {
        // Re-register for query notification SqlDependency Change events.
        SendNotifications();
    }
}

    //Create the Hub
    //To create a Hub, create a class that derives from Microsoft.Aspnet.Signalr.Hub. 

//Alias that can call class from javascript. - i.e.  var hub = con.createHubProxy('DisplayMessage');
[HubName("DisplayMessage")]
public class NotificationsHub : Hub //Adding [:Hub] let c# know that this is a Hub 
{
    //In this example, a connected client can call the NotifyAllClients method, and when it does, the data received is broadcasted to all connected clients.

    //Create NotifyAllClients Method
    //public means accessible to other classes
    //void means its not returning any data
    public void NotifyAllClients(string msg)
    {
        IHubContext context = GlobalHost.ConnectionManager.GetHubContext<NotificationsHub>();
        //When this method gets called, every single client has a function displayNotification() that is going to be executed
        //msg is the data that is going to be displayed to all clients.
        context.Clients.All.displayNotification(msg);                                                       
    }