Code

var copy = new Diagram();
copy.LoadFromString(diagram.SaveToString());

var currentLayer = -1;
var currentX = float.NegativeInfinity;
var nodes = copy.Nodes.Clone();
nodes.Sort((n1, n2) =>
	n1.Bounds.X.CompareTo(n2.Bounds.X));
foreach (var node in nodes)
{
	var x = node.Bounds.X;
	if (x != currentX)
	{
		currentLayer++;
		currentX = x;
	}
	node.LayoutTraits[LayeredLayoutTraits.Layer] = currentLayer;
}

var ll = new LayeredLayout();
ll.StraightenLongLinks = true;
ll.EnableCustomLayers = true;
ll.Orientation = MindFusion.Diagramming.Layout.Orientation.Horizontal;
ll.Arrange(copy);

for (int i = 0; i < diagram.Nodes.Count; i++)
{
	var n = diagram.Nodes[i];
	var c = copy.Nodes[i];
	n.Move(n.Bounds.X, c.Bounds.Y);
}

for (int i = 0; i < diagram.Links.Count; i++)
{
	var l = diagram.Links[i];
	var c = copy.Links[i];
	if (c.SegmentCount == 1)
	{
		l.SegmentCount = 1;
	}
	else
	{
		// there should be three segments if StraightenLongLinks is set
		l.AutoRoute = false;
		l.Shape = LinkShape.Polyline;
		l.SegmentCount = 3;
		var bend1 = c.ControlPoints[1];
		var bend2 = c.ControlPoints[2];
		float dist = Utilities.Distance(
			l.Origin.GetCenter(), l.Destination.GetCenter());
		float dx = l.Destination.GetCenter().X - l.Origin.GetCenter().X;
		dx /= dist;
		bend1.X = l.StartPoint.X + dx * 10;
		bend2.X = l.EndPoint.X - dx * 10;
		l.ControlPoints[1] = bend1;
		l.ControlPoints[2] = bend2;
		l.UpdateFromPoints();
	}
} 

Code

var copy = new Diagram();
copy.LoadFromString(diagram.SaveToString());

var ll = new LayeredLayout();
ll.EnforceLinkFlow = true;
ll.Arrange(copy);

for (int i = 0; i < diagram.Nodes.Count; i++)
{
	var n = diagram.Nodes[i];
	var c = copy.Nodes[i];
	n.Move(n.Bounds.X, c.Bounds.Y);
}