Custom selection extension
ToggleDockWinBtn.vb
' Copyright 2012 ESRI
' 
' All rights reserved under the copyright laws of the United States
' and applicable international laws, treaties, and conventions.
' 
' You may freely redistribute and use this sample code, with or
' without modification, provided you include the original copyright
' notice and use restrictions.
' 
' See the use restrictions.
' 

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.Text
Imports System.IO
Imports ESRI.ArcGIS.esriSystem
Imports ESRI.ArcGIS.Framework

Namespace SelectionSample
  Public Class ToggleDockWinBtn
    Inherits ESRI.ArcGIS.Desktop.AddIns.Button

  Public Sub New()

  End Sub

  Protected Overrides Sub OnClick()
      Dim dockWindow As ESRI.ArcGIS.Framework.IDockableWindow
      dockWindow = SelectionExtension.GetSelectionCountWindow()

    If dockWindow Is Nothing Then
    Return
    End If

    dockWindow.Show((Not dockWindow.IsVisible()))
  End Sub

  Protected Overrides Sub OnUpdate()
    Me.Enabled = SelectionExtension.IsExtensionEnabled()
  End Sub
  End Class

End Namespace