Singleton being instantiated multiple times

Add-in Express™ Support Service
That's what is more important than anything else

Singleton being instantiated multiple times
 
Mark Amans




Posts: 11
Joined: 2011-02-09
I created a shared memory object as a singleton using the advice I saw here: http://www.add-in-express.com/forum/read.php?FID=10&TID=9544

When I open a 2nd tab or window, a new instance of the singleton is being created. When I open a 3rd tab or window, it re-uses the singleton from the first tab. When I open a 4th tab it re-uses the singleton from the 2nd tab. I've tried this with up to 15 tabs open and it always follows the same pattern:

Singleton Instance 1: tab 1, tab 3, tab 5, tab 10
Singleton Instance 2: tab 2, tab 4, tab 8, tab 14
Singleton Instance 3: tab 6, tab 7, tab 9, tab 15
Singleton Instance 4: tab 11, tab 12, tab 13

I don't understand how the singleton is being instantiated more than once. Can anyone shed any light on this?

My singleton class is as follows:

Imports System
Imports System.Runtime.InteropServices

<ComVisible(False)> _
Public Class SharedData1
    Private Shared _instance As SharedData1
    Private Shared ReadOnly _lock As Object = New Object()
    Private Shared _date As DateTime
    Private Shared _string As String
    Public Property DummyString() As String
        Get
            Return _string
        End Get
        Set(ByVal value As String)
            _string = value
        End Set
    End Property


    Protected Overrides Sub Finalize()
        System.Diagnostics.Debug.WriteLine("Finalizing SharedData1: " & _date.Hour & ":" & _date.Minute & ":" & _date.Second & "." & _date.Millisecond)
    End Sub

    Private Sub New()
        ' Private constructor prevents instantiation outside the class
    End Sub

    Public Shared ReadOnly Property Instance() As SharedData1
        Get
            SyncLock (_lock)
                If (SharedData1._instance Is Nothing) Then
                    SharedData1._instance = New SharedData1()
                    _date = DateTime.Now
                    System.Diagnostics.Debug.WriteLine("Creating new SharedData1: " & _date.Hour & ":" & _date.Minute & ":" & _date.Second & "." & _date.Millisecond)
                Else
                    System.Diagnostics.Debug.WriteLine("SharedData1 already exists: " & _date.Hour & ":" & _date.Minute & ":" & _date.Second & "." & _date.Millisecond)
                End If
            End SyncLock
            Return SharedData1._instance
        End Get
    End Property

End Class


I'm using ADXIE 2011 with Visual Studio 2010
Posted 14 May, 2012 18:52:54 Top
Sergey Grischenko


Add-in Express team


Posts: 7202
Joined: 2004-07-05
Hi Mark,

Please open several IE tabs and then open the Task Manager. You will see several IE processes running at the same time. The fact is that IE opens tabs in different sub-processes and/or threads. That is why the shared memory object may be created more than once (it is typical for IE8 - IE10).
Posted 15 May, 2012 12:18:07 Top
Mark Amans




Posts: 11
Joined: 2011-02-09
Hi Sergey,

Then how can I share data between different instances of the toolbar if I can't use a single object like a singleton? Where should I store the data the I want to share?

Thanks,
Mark
Posted 15 May, 2012 13:27:20 Top
Sergey Grischenko


Add-in Express team


Posts: 7202
Joined: 2004-07-05
Hi Mark,

You can store data in a file as shown in the 'Synchronize settings' example.
Posted 16 May, 2012 10:23:09 Top
Sergey Grischenko


Add-in Express team


Posts: 7202
Joined: 2004-07-05
Mark,
you can also use the GetModuleByIndex, GetModuleByThread, GetModuleCount and GetModulesByTypeName (static) methods of the 'ADXIEModule' class to access your modules directly.
Posted 16 May, 2012 10:27:31 Top
Mark Amans




Posts: 11
Joined: 2011-02-09
I ended up using a MemoryMappedFile to share the data between the toolbar instances and it's working fine.
Posted 16 May, 2012 17:20:13 Top
Sergey Grischenko


Add-in Express team


Posts: 7202
Joined: 2004-07-05
Hi Mark,

Add-in Express provides the 'ADXIESharedMemory' class that implements file mapping. It is used in the 'Synchronize settings' example.
Posted 17 May, 2012 10:26:38 Top