Add article, code, toc, and redirects (#1343)

dotnet-desktop-guide/net/wpf/events/snippets/object-lifetime-events/vb/MainWindow.xaml.vb

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+'<LifetimeEventsCodeBehind>
+Partial Public Class MainWindow
+    Inherits Window
+
+    Public Sub New()
+        InitializeComponent()
+    End Sub
+
+    ' Handler for the Initialized lifetime event (attached in XAML).
+    Private Sub InitHandler(sender As Object, e As EventArgs)
+        Debug.WriteLine($"Initialized event on {CType(sender, FrameworkElement).Name}.")
+    End Sub
+
+    ' Handler for the Loaded lifetime event (attached in XAML).
+    Private Sub LoadHandler(sender As Object, e As RoutedEventArgs)
+        Debug.WriteLine($"Loaded event on {CType(sender, FrameworkElement).Name}.")
+    End Sub
+
+    ' Handler for the Unloaded lifetime event (attached in XAML).
+    Private Sub UnloadHandler(sender As Object, e As RoutedEventArgs)
+        Debug.WriteLine($"Unloaded event on {CType(sender, FrameworkElement).Name}.")
+    End Sub
+
+    Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
+        ' Remove nested controls.
+        canvas.Children.Clear()
+    End Sub
+End Class
+
+' Custom control.
+Public Class ComponentWrapper
+    Inherits ComponentWrapperBase
+End Class
+
+' Custom base control.
+Public Class ComponentWrapperBase
+    Inherits StackPanel
+
+    Public Sub New()
+        ' Attach handlers for the lifetime events.
+        AddHandler Initialized, AddressOf InitHandler
+        AddHandler Loaded, AddressOf LoadHandler
+        AddHandler Unloaded, AddressOf UnloadHandler
+    End Sub
+
+    ' Handler for the Initialized lifetime event (attached in code-behind).
+    Private Sub InitHandler(sender As Object, e As EventArgs)
+        Debug.WriteLine("Initialized event on componentWrapperBase.")
+    End Sub
+
+    ' Handler for the Loaded lifetime event (attached in code-behind).
+    Private Sub LoadHandler(sender As Object, e As RoutedEventArgs)
+        Debug.WriteLine("Loaded event on componentWrapperBase.")
+    End Sub
+
+    ' Handler for the Unloaded lifetime event (attached in code-behind).
+    Private Sub UnloadHandler(sender As Object, e As RoutedEventArgs)
+        Debug.WriteLine("Unloaded event on componentWrapperBase.")
+    End Sub
+End Class
+
+'Output:
+'Initialized event on textBox1.
+'Initialized event on textBox2.
+'Initialized event on componentWrapperBase.
+'Initialized event on componentWrapper.
+'Initialized event on outerStackPanel.
+
+'Loaded event on outerStackPanel.
+'Loaded event on componentWrapperBase.
+'Loaded event on componentWrapper.
+'Loaded event on textBox1.
+'Loaded event on textBox2.
+
+'Unloaded event on outerStackPanel.
+'Unloaded event on componentWrapperBase.
+'Unloaded event on componentWrapper.
+'Unloaded event on textBox1.
+'Unloaded event on textBox2.
+'</LifetimeEventsCodeBehind>