WPF VB.Net

  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="Window1" Height="100" Width="200">
  
    
    
  


//File:Window.xaml.vb
Imports System.Windows
Imports System
Namespace WpfApplication1
  Public Partial Class Window1
    Inherits Window
    Public Sub New()
      InitializeComponent()
      DataContextProperty.OverrideMetadata(GetType(Window1), New FrameworkPropertyMetadata(100.0, New PropertyChangedCallback(AddressOf DataContext_PropertyChanged)))
    End Sub
    Private Shared Sub DataContext_PropertyChanged(d As DependencyObject, e As DependencyPropertyChangedEventArgs)
      Dim msg As String = String.Format("DataContext changed.{0}{0}Old Value: {1}{0}New Value: {2}", Environment.NewLine, e.OldValue.ToString(), e.NewValue.ToString())
      MessageBox.Show(msg, "changed")
    End Sub
    Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
      DataContext = tbxUserText.Text
    End Sub
  End Class
End Namespace