Fire an event when an element gains and loses focus.

     

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:custom="clr-namespace:WpfApplication1"  
    Title="gotfocusLostfocusEffectUsingEvent" Height="400" Width="450"
    >
  <StackPanel>
    <StackPanel.Resources>
      <Style TargetType="{x:Type Button}">
        <Setter Property="Height" Value="20"/>
        <Setter Property="Width" Value="250"/>
        <Setter Property="HorizontalAlignment" Value="Left"/>
      </Style>
    </StackPanel.Resources>
    <Button
        GotFocus="OnGotFocusHandler"
        LostFocus="OnLostFocusHandler">Click Or Tab To Give Keyboard Focus</Button>
    <Button
        GotFocus="OnGotFocusHandler"
        LostFocus="OnLostFocusHandler">Click Or Tab To Give Keyborad Focus</Button>
  </StackPanel>
</Window>

//File:Window.xaml.vb

Imports System
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Windows.Media
Imports System.Windows.Input

Namespace WpfApplication1
  Public Partial Class Window1
    Inherits Window
    Public Sub New()
      InitializeComponent()
    End Sub
    Private Sub OnGotFocusHandler(sender As Object, e As RoutedEventArgs)
      Dim tb As Button = TryCast(e.Source, Button)
      tb.Background = Brushes.Red
    End Sub
    Private Sub OnLostFocusHandler(sender As Object, e As RoutedEventArgs)
      Dim tb As Button = TryCast(e.Source, Button)
      tb.Background = Brushes.White
    End Sub
  End Class
End Namespace

1.	Get event sender from event
2.	Handle the ContentRendered event
3.	Find source element of an element in event handler by casting
4.	Add an event handler to an element using code
5.	Halting event routing with Handled
6.	Security Exception
7.	Throw Handled Exception
8.	Check handler event sender
9.	Do event based on button name
10.	Add event handler to StackPanel in StackPanel resource
11.	Add a PropertyChangedValueCallback to Any Dependency Property
12.	Handle a Button Click with Shared button click handler
13.	DispatcherTimer and EventHandler
14.	Thumb DragStarted and DragCompleted event handler
15.	Set interval and event handler for DispatcherTimer
16.	Get the event sender name
17.	Event firing sequence
18.	Cancel event by setting CanExecute and Handled to false
19.	Event sender, event source and event original source
20.	Cast event sender to a control

Fire an event when an element gains and loses focus. : Event « Windows Presentation Foundation « VB.Net

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