Untitled

private void ToggleButton_Click(object sender, RoutedEventArgs e)
{
    if (toggleButton.IsChecked == true)
    {
        foreach (TabItem tabItem in tabControl.Items)
        {
            tabItem.Visibility = Visibility.Collapsed;
        }
    }
    else
    {
        foreach (TabItem tabItem in tabControl.Items)
        {
            tabItem.Visibility = Visibility.Visible;
        }
    }
}