How to call a button click event from another method
You can easily do it by the following piece of code (assuming that name of your button is btnButton):
btnButton.PerformClick();
You can call the button_click event by simply passing the arguments to it:
private void SubGraphButton_Click(object sender, RoutedEventArgs args)
{
}
private void ChildNode_Click(object sender, RoutedEventArgs args)
{
SubGraphButton_Click(sender, args);
}