Application Events Help

[HJohn1]

In VBA I have a routine that used the Application's AppActivate and AppDeactivate events.  Also, in VBA I used the BeginCommand and EndCommand events.  Now, in .NET I am not sure how to use them.  I put together a class to use these events in .NET.  It seems to be working, but I am not sure of what I am doing.  Could someone who has been using these events in .NET take a look at the following class and let me know what needs to be improved or changed.  Basically, I am looking to achieve something similar to what I was using in VBA.  Any help will be greatly appreciated.

Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.EditorInput
Imports Autodesk.AutoCAD.Runtime

Public Class MyAppEventClass
    Implements Autodesk.AutoCAD.Runtime.IExtensionApplication

    Public Sub Initialize() Implements Autodesk.AutoCAD.Runtime.IExtensionApplication.Initialize

        AddHandler Application.DocumentManager.DocumentCreated, AddressOf Me.CallBack_DocumentCreated

        Call Me.IntializeEvents()

    End Sub

    Public Sub Terminate() Implements Autodesk.AutoCAD.Runtime.IExtensionApplication.Terminate
        'I am not sure if I really need to remove the handlers
    End Sub

    Private Sub CallBack_CommandEnded(ByVal sender As Object, ByVal e As CommandEventArgs)
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        ed.WriteMessage(vbCrLf & "A command is about to end.")
    End Sub

    Private Sub CallBack_CommandWillStart(ByVal sender As Object, ByVal e As CommandEventArgs)
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        ed.WriteMessage(vbCrLf & "A command is about to start.")
    End Sub

    Private Sub CallBack_DocumentCreated(ByVal sender As Object, ByVal e As DocumentCollectionEventArgs)

        Me.IntializeEvents()

    End Sub
    Private Sub CallBack_DocumentToBeActivated(ByVal seneder As Object, ByVal e As DocumentCollectionEventArgs)
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        ed.WriteMessage(vbCrLf & "A document is about to be activated.")
    End Sub
    Private Sub CallBack_DocumentToBeDeactivated(ByVal seneder As Object, ByVal e As DocumentCollectionEventArgs)
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        ed.WriteMessage(vbCrLf & "A document is about to be deactivated.")
    End Sub
    Private Sub CallBack_DocumentActivationChanged(ByVal seneder As Object, ByVal e As DocumentActivationChangedEventArgs)
        Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
        ed.WriteMessage(vbCrLf & "Document activation has changed.")
    End Sub

    Private Sub IntializeEvents()
        Dim Doc As Document

        For Each Doc In Application.DocumentManager

            AddHandler Doc.CommandWillStart, AddressOf Me.CallBack_CommandWillStart

            AddHandler Doc.CommandEnded, AddressOf Me.CallBack_CommandEnded

        Next

        AddHandler Application.DocumentManager.DocumentToBeActivated, AddressOf Me.CallBack_DocumentToBeActivated

        AddHandler Application.DocumentManager.DocumentToBeDeactivated, AddressOf Me.CallBack_DocumentToBeDeactivated

        AddHandler Application.DocumentManager.DocumentActivationChanged, AddressOf Me.CallBack_DocumentActivationChanged

    End Sub

    Private Sub TerminateEvents()
        'Handler removal here
    End Sub

End Class

[leefsma]

Hi John,

Your VB.Net events do not work because you need to keep a member variable inside your class for each object you are listening events from, otherwise .Net will not maintain the callback on an object that is garbage collected.

Here is a small example. Also remember that .Net classes are instanciated once per document, the first time you run a command in that document, so this behavior may influence your events as they depend on member variables.

if you want to have an application wide event that doesn't relate directly to a specific document, you can use the keyword "Shared", so the member is instanciated only once.

Public Class PerDocManager
    Implements IExtensionApplication

    Private Shared _DocumentManager As DocumentCollection

    '///////////////////////////////////////////////////////////////////////////////////////////////////
    '//
    '//
    '///////////////////////////////////////////////////////////////////////////////////////////////////
    Public Sub Initialize() Implements IExtensionApplication.Initialize
        
        'Un-comment if you want to demandload the dll after the first loading
        'Otherwise run command "RegisterMe" to manually register for demandloading
        'Run command Unregister to delete demandloading registry entry
        'RegisterMe()

        _DocumentManager = Application.DocumentManager

        AddHandler _DocumentManager.DocumentActivated, AddressOf DocumentActivated

        AddHandler _DocumentManager.DocumentToBeDestroyed, AddressOf DocumentToBeDestroyed

    End Sub

    '///////////////////////////////////////////////////////////////////////////////////////////////////
    '//
    '//
    '///////////////////////////////////////////////////////////////////////////////////////////////////
    Public Sub Terminate() Implements IExtensionApplication.Terminate

        RemoveHandler _DocumentManager.DocumentActivated, AddressOf DocumentActivated

        RemoveHandler _DocumentManager.DocumentToBeDestroyed, AddressOf DocumentToBeDestroyed

    End Sub

I hope it helps.

Philippe Leefsma
Developer Consultant
Developer Technical Services
Global Subscription & Support
 

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