//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