Dim winds As List(Of WPFWindow) = New List(Of WPFWindow)()
Private Sub C1DockControl_ItemDockModeChanged(sender As Object, e As C1.WPF.Docking.ItemDockModeChangedEventArgs)
　　winds.Clear()
　　For Each wind In Application.Current.Windows
　　　　If TypeOf wind Is WPFWindow Then
　　　　　　winds.Add(CType(wind, WPFWindow))
　　　　End If
　　Next
End Sub

Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
　　Dim oldName As String = CStr(A_Tab.Header)
　　A_Tab.Header = "NewName"

　　For Each wind In winds
　　　　If CStr(wind.Content) = oldName And AATab.IsSelected Then
　　　　　　Dim bdr As Border = CType(VTreeHelper.GetParentOfType(AATab, GetType(Border)), Border)
　　　　　　Dim g As Grid = CType(bdr.Parent, Grid)
　　　　　　g = CType(g.Parent, Grid)
　　　　　　bdr = CType(g.Children(1), Border)
　　　　　　g = CType(bdr.Child, Grid)
　　　　　　Dim cc As ContentControl = CType(g.Children(0), ContentControl)
　　　　　　Dim cp As ContentPresenter = CType(VisualTreeHelper.GetChild(cc, 0), ContentPresenter)
　　　　　　Dim tb As TextBlock = CType(VisualTreeHelper.GetChild(cp, 0), TextBlock)
　　　　　　tb.Text = CStr(A_Tab.Header)
　　　　End If
　　Next
End Sub

List winds = new List();
private void C1DockControl_ItemDockModeChanged(object sender, C1.WPF.Docking.ItemDockModeChangedEventArgs e)
{
　　winds.Clear();
　　foreach (var window in Application.Current.Windows)
　　{
　　　　if (window is WPFWindow)
　　　　{
　　　　　　winds.Add((WPFWindow)window);
　　　　}
　　}
}

private void button_Click(object sender, RoutedEventArgs e)
{
　　string oldName = (string)A_Tab.Header;
　　A_Tab.Header = "NewName";

　　foreach (WPFWindow wind in winds)
　　{
　　　　if ((string)wind.Content == oldName && AATab.IsSelected)
　　　　{
　　　　　　Border bdr = (Border)VTreeHelper.GetParentOfType(AATab, typeof(Border));
　　　　　　Grid g = (Grid)bdr.Parent;
　　　　　　g = (Grid)g.Parent;
　　　　　　bdr = (Border)g.Children[1];
　　　　　　g = (Grid)bdr.Child;
　　　　　　ContentControl cc = (ContentControl)g.Children[0];
　　　　　　ContentPresenter cp = (ContentPresenter)VisualTreeHelper.GetChild(cc, 0);
　　　　　　TextBlock tb = (TextBlock)VisualTreeHelper.GetChild(cp, 0);
　　　　　　tb.Text = (string)A_Tab.Header;
　　　　}
　　}
}