sdk/samples/all in on code/Visual Studio 2010/VBWPFMVVMPractice/AttachedBehavior/ShutdownBehavior.vb

   1 '****************************** Module Header ******************************\
   2 ' Module Name:  ShutdownBehavior.vb
   3 ' Project:          VBWPFMVVMPractice
   4 ' Copyright (c) Microsoft Corporation.
   5 '
   6 ' The ShutdownBehavior class is an attached behavior that is used to shut down the application.
   7 '
   8 ' This source is subject to the Microsoft Public License.
   9 ' See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
  10 ' All other rights reserved.
  11 '
  12 ' THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
  13 ' EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
  14 ' WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
  15 '***************************************************************************/
  16
  17 Public Class ShutdownBehavior
  18     Inherits DependencyObject
  19
  20     Public Shared Function GetForceShutdown(ByVal obj As DependencyObject) As Nullable(Of Boolean)
  21         Return DirectCast(obj.GetValue(ShutdownBehavior.ForceShutdownProperty), Nullable(Of Boolean))
  22     End Function
  23
  24     Public Shared Sub SetForceShutdown(ByVal obj As DependencyObject, ByVal value As Nullable(Of Boolean))
  25         obj.SetValue(ShutdownBehavior.ForceShutdownProperty, value)
  26     End Sub
  27
  28     ' Using a DependencyProperty as the backing store for ForceShutdown.  This enables
  29     ' animation, styling, binding, etc...
  30     Public Shared ReadOnly ForceShutdownProperty As DependencyProperty =
  31         DependencyProperty.RegisterAttached(
  32             "ForceShutdown",
  33             GetType(Nullable(Of Boolean)),
  34             GetType(ShutdownBehavior),
  35             New UIPropertyMetadata(
  36                 Nothing,
  37                 Function(sender As DependencyObject, e As DependencyPropertyChangedEventArgs)
  38                     ShutdownBehavior.OnPropertyChangedCallBack(sender, e)
  39                 End Function))
  40
  41     ''' <summary>
  42     ''' MenuItem's Click event handler
  43     ''' </summary>
  44     Private Shared Sub mnu_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
  45
  46         ' If the ForceShutdown attached proerty value set on the MenuItem is true, exit the
  47         ' application immediately.
  48         If ShutdownBehavior.GetForceShutdown(TryCast(sender, DependencyObject)).Value Then
  49             Application.Current.Shutdown()
  50
  51             ' If the ForceShutdown attached proerty value set on the MenuItem is false, show a
  52             ' messagebox before exiting the application.
  53         ElseIf (Not ShutdownBehavior.GetForceShutdown(TryCast(sender, DependencyObject)).Value AndAlso
  54                 (MessageBox.Show("Are you sure to exit the application?",
  55                                  "Exit", MessageBoxButton.OKCancel) = MessageBoxResult.OK)) Then
  56             Application.Current.Shutdown()
  57         End If
  58     End Sub
  59
  60     ''' <summary>
  61     ''' The ForceShutdown property's PropertyChangedCallback method.
  62     ''' In this method, get the MenuItem the attached property is set on and subscribe to the
  63     ''' Click event of the MenuItem.
  64     ''' </summary>
  65     Private Shared Sub OnPropertyChangedCallBack(ByVal sender As DependencyObject,
  66                                                  ByVal e As DependencyPropertyChangedEventArgs)
  67         Dim mnu As MenuItem = TryCast(sender, MenuItem)
  68
  69         ' This ensures the Click event on the MenuItem is subscribed to only once.
  70         If (Not mnu Is Nothing) Then
  71             RemoveHandler mnu.Click, New RoutedEventHandler(AddressOf ShutdownBehavior.mnu_Click)
  72             AddHandler mnu.Click, New RoutedEventHandler(AddressOf ShutdownBehavior.mnu_Click)
  73         End If
  74     End Sub
  75
  76 End Class
  77