OnConnected和OnDisconnected事件触发两次¿

Question

在以下代码中，当我连接或断开客户端时，事件OnConnected和Disconnected将触发两次。怎么避免这个？ 我有所有组件的最后一个版本。

Imports Microsoft.AspNet.SignalR
Imports Microsoft.Owin.Cors
Imports Microsoft.Owin.Hosting
Imports Owin
Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim url As String = "http://localhost:8080/arc/"
        WebApp.Start(url)
    End Sub
End Class
Class Startup
    Public Sub Configuration(app As IAppBuilder)
        app.UseCors(CorsOptions.AllowAll)
        app.MapSignalR()
    End Sub
End Class
Public Class MyHub
    Inherits Hub
    Public Sub Send(name As String, message As String)
        Clients.All.addMessage(name, message)
    End Sub
    Public Overrides Function OnConnected() As Task
        Debug.Print("Client connected: " + Context.ConnectionId)
        Return MyBase.OnConnected()
    End Function
    Public Overrides Function OnDisconnected(stopCalled As Boolean) As Task
        Debug.Print("Client DISconnected: " + Context.ConnectionId)
        Return MyBase.OnDisconnected(True)
    End Function
   End Class

Vb.net中的客户端代码如下：

Imports Microsoft.AspNet.SignalR.Client
Imports System.ComponentModel
Imports Microsoft.AspNet.SignalR.Client.Hubs

Partial Public Class MainWindow
    Inherits Window
    Implements INotifyPropertyChanged
    Public connection As HubConnection = New HubConnection("http://localhost:8080/arc/")
    Public myHub As IHubProxy

    Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
        DataContext = Me
        connection = New HubConnection("http://localhost:8080/arc/")

        myHub = connection.CreateHubProxy("myHub")
        myHub.On(Of String)("addMessage", AddressOf addMessage)
    End Sub

    Async Sub btnShowSignal_Click(sender As Object, e As RoutedEventArgs)
        Await connection.Start()
    End Sub