This worked in my test:

private void button2_Click(object sender, EventArgs e)
{
	diagram.SelectionOnTop = false;

	foreach (DiagramNode node in diagram.Nodes)
		node.ZTop();
}
 

Changing the Z order might not be possible in some contexts; in response to what event does your code run?

Hi,

You could directly reorder the elements of Diagram.Items to set the Z order quickly. However each item keeps its own index within that collection in a private field, and unfortunately there is no public method to get these indices in sync with the new Items order. We can add such method for the next release, and for now you could try some workarounds. E.g. after reordering Diagram.Items, execute an empty CompositeCmd created using the constructor that takes a 'saveZOrder' argument, and then immediately undo it. That should update the items Z indices according to the Items order. Another possibility is to call ZTop followed by ZBottom for the first item to update the Z indices for all other items.

I hope that helps,
Stoyan