Private m_objDTE As EnvDTE.DTE

Public Sub OnConnection(ByVal application As Object, _
   ByVal connectMode As Extensibility.ext_ConnectMode, _
   ByVal addInInst As Object, ByRef custom As System.Array) _
   Implements Extensibility.IDTExtensibility2.OnConnection

   ' Note: 
   ' - Add the following references to the project:
   ' System.Windows.Forms

   ' - Add the following Imports to this file:
   ' Imports System.ComponentModel
   ' Imports System.ComponentModel.Design
   ' Imports System.Windows.Forms

   Dim objWindow As Window
   Dim objIDesignerHost As IDesignerHost
   Dim objIComponent As IComponent
   Dim colPropertyDescriptorCollection As PropertyDescriptorCollection
   Dim objPropertyDescriptor As PropertyDescriptor
   Dim objIContainer As IContainer
   Dim objIServiceProvider As IServiceProvider
   Dim objISelectionService As ISelectionService

   Try

      m_objDTE = DirectCast(application, EnvDTE.DTE)

      If connectMode = ext_ConnectMode.ext_cm_AfterStartup Then

         ' Get the active window
         ' Note: ensure that a Design window is active before running this code
         ' Note also that there is a bug in Visual Studio .NET
 and the ActiveWindow property 
         ' returns the first window of the document that was open, which could be
         ' the code window, and not the active window as it would be expected.

         objWindow = m_objDTE.ActiveDocument.ActiveWindow

         ' Get the designer host
         objIDesignerHost = DirectCast(objWindow.Object, IDesignerHost)

         ' Get the service provider
         objIServiceProvider = DirectCast(objIDesignerHost, IServiceProvider)

         ' Get the selection service
         objISelectionService = DirectCast(objIServiceProvider.GetService( _
            GetType(ISelectionService)), ISelectionService)

         ' Show the count of selected controls
         MessageBox.Show("The active designer has " & _
            objISelectionService.SelectionCount.ToString() & " control(s) selected.")

         ' Get the container
         objIContainer = objIDesignerHost.Container

         ' Iterate the components in a linear way (not hierarchically)
         For Each objIComponent In objIContainer.Components

            If TypeOf objIComponent Is Form Then

               ' This component is the form itself. You could cast it to a Form object
               ' and use its Controls collection to iterate the controls in a hierarchical way
               ' Skip it for the purpose of this sample.

            ElseIf TypeOf objIComponent Is UserControl Then

               ' Same previous comment, for the case of UserControls

            Else ' It is a control of the form, or a component of the component tray

               colPropertyDescriptorCollection = TypeDescriptor.GetProperties(objIComponent)

               objPropertyDescriptor = colPropertyDescriptorCollection.Item("Tag")

               If Not (objPropertyDescriptor Is Nothing) Then
                  objPropertyDescriptor.SetValue(objIComponent, "Tag modified")
               End If

            End If

         Next

      End If

   Catch objException As Exception

      MessageBox.Show(objException.ToString)

   End Try

End Sub