sqldependency on change not always firing - vb.net

Question

Here is my code:
Public Sub RegisterNotification()
Dim conStr As String = ConfigurationManager.ConnectionStrings("sqlConString").ConnectionString
Dim sqlCommand As String = "SELECT [ID],[Description], [CreateDate], [NoteTypeID] from [note].[Notes]"
Using con As New SqlConnection(conStr)
Dim cmd As New SqlCommand(sqlCommand, con)
If con.State <> System.Data.ConnectionState.Open Then
con.Open()
End If
cmd.Notification = Nothing
Dim sqlDep As New SqlDependency(cmd)
AddHandler sqlDep.OnChange, AddressOf sqlDep_OnChange
Using reader As SqlDataReader = cmd.ExecuteReader()
End Using
End Using
End Sub
Private Sub sqlDep_OnChange(sender As Object, e As SqlNotificationEventArgs)
If e.Type = SqlNotificationType.Change Then
Dim sqlDep As SqlDependency = TryCast(sender, SqlDependency)
'Dim id
RemoveHandler sqlDep.OnChange, AddressOf sqlDep_OnChange
If e.Info = 1 Then
Dim notificationHub = GlobalHost.ConnectionManager.GetHubContext(Of NotificationHub)()
notificationHub.Clients.All.notify("added")
RegisterNotification()
'GetNotificationList(0, 1)
End If
End If
End Sub
Global.asax code:
Protected Sub Application_Start()
Try
Dim _obj As New DAL.sap.Register
_obj.Register()
AreaRegistration.RegisterAllAreas()
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters)
RouteConfig.RegisterRoutes(RouteTable.Routes)
BundleConfig.RegisterBundles(BundleTable.Bundles)
WebSecurity.InitializeDatabaseConnection("DefaultConnection", "webpages_UserProfile", "UserId", "UserName", True)
SqlDependency.Start(con)
Catch ex As Exception
End Try
End Sub
Protected Sub Session_Start(sender As Object, e As EventArgs)
Try
Dim NC As New NotificationComponent()
NC.RegisterNotification()
Catch ex As Exception
End Try
End Sub
Protected Sub Application_End()
Try
SqlDependency.Stop(con)
Catch ex As Exception
End Try
End Sub
Startup code:
<Assembly: OwinStartupAttribute(GetType(www.Startup))>
Namespace www
Partial Public Class Startup
Public Sub Configuration(app As IAppBuilder)
app.MapSignalR()
End Sub
End Class
End Namespace
My problem is sqldep_onchange not always firing. Sometimes it works perfectly but sometimes nothing happen. is it a bug or something like that? what i'm doing wrong?

Answer 1

It looks like everything is correct, although my VB is extremely rusty, I would try removing the if on the SqlNotificationType and see if that helps, it might be too restricting, I would also make sure that its actually the dependency that is not firing rather an something else swallowing it later on down the chain. Also what happens if your TryCast fails? Since its not in a try it will not throw and your notifications will not fire and your new handler will not be added.
Private Sub sqlDep_OnChange(sender As Object, e As SqlNotificationEventArgs)
If e.Type = SqlNotificationType.Change Then
Dim sqlDep As SqlDependency = TryCast(sender, SqlDependency)
'Dim id
Delete --> ***RemoveHandler sqlDep.OnChange, AddressOf sqlDep_OnChange*** <--Delete
If e.Info = 1 Then
Dim notificationHub = GlobalHost.ConnectionManager.GetHubContext(Of NotificationHub)()
notificationHub.Clients.All.notify("added")
RegisterNotification()
'GetNotificationList(0, 1)
End If
End If
End Sub