Code

 //----------
        // adjust DIAGRAM HEIGHT as lanes are added / dropped to compact the diagram around lanes

        // refering diagram
        //Diagram diagramPB = diagramView.Diagram;

        // finding last stage
        ShapeNode lastShapeNode = diagramPB.FindNodeById("Stage " + extVarStages) as ShapeNode;

        // check if last shape node's bottom is greater than diagram height,
        // if so increase diagram height to last shape node's bottom
        if (lastShapeNode.Bounds.Bottom > diagramHeight)
        {

            diagramHeight = Convert.ToInt32(lastShapeNode.Bounds.Bottom);
            diagramPB.Bounds = new System.Drawing.RectangleF(0, 0, diagramWidth, diagramHeight);
        }

        // check if last shape node's bottom is lesser than diagram height,
        // if so decrease diagram height to last shape node's bottom
        if (lastShapeNode.Bounds.Bottom < diagramHeight)
        {

            diagramHeight = Convert.ToInt32(lastShapeNode.Bounds.Bottom);
            diagramPB.Bounds = new System.Drawing.RectangleF(0, 0, diagramWidth, diagramHeight);
        }

        //------------