private void TabControlMenuItem_Click(object sender, RoutedEventArgs e)
{
BindingExpression be = ((MenuItem)sender).GetBindingExpression(HeaderedItemsControl.HeaderProperty);
WorkspaceViewModel wsvm = (WorkspaceViewModel)be.DataItem;
WorkspaceTabs.SelectedIndex = dynamoViewModel.Workspaces.IndexOf(wsvm);
ToggleWorkspaceTabVisibility(WorkspaceTabs.SelectedIndex);
}