Align Pipes at bottom

This is an old Revit macro I've created to align pipes to the bottom (BOP or BOI).
It asks for a pipe to be used as reference and the pipes to be aligned.

You need to create a new macro and paste the code below replacing all the content of the file. After this you will se a module named Align_Pipe

The module should look like this

Here is the code:

/*
 * Created by SharpDevelop.
 * User: pderendinger
 * Date: 10/5/2015
 * Time: 5:40 PM
 * 
 * To change this template use Tools | Options | Coding | Edit Standard Headers.
 */
using System;
using Autodesk.Revit.UI;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI.Selection;
using System.Collections.Generic;
using System.Linq;

namespace Align
{
    [Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)]
    [Autodesk.Revit.DB.Macros.AddInId("7E4D77C7-4626-4D7A-AAA7-44F7ADD7A38B")]
 public partial class ThisApplication
 {
  private void Module_Startup(object sender, EventArgs e)
  {

  }

  private void Module_Shutdown(object sender, EventArgs e)
  {

  }

  #region Revit Macros generated code
  public void Align_Pipe()

  {
   UIDocument uidoc = this.ActiveUIDocument;
   Document doc = uidoc.Document;
   
   TaskDialog.Show("Select Reference","Select Pipe as Reference");
   
   Reference pr = uidoc.Selection.PickObject(ObjectType.Element);
   Element element = doc.GetElement(pr);
   
  double prodia= 0; 
  double proff= 0;
   if (element.Category.Name == "Pipes")
   {
   prodia= element.LookupParameter("Outside Diameter").AsDouble();
   proff= element.LookupParameter("Offset").AsDouble();
   }
   else
   {
    TaskDialog.Show("Error","Select a Pipes to align");
   }
   
   double h = proff - (prodia/2);
   
   TaskDialog.Show("Select Elements","Select Pipes to align");
   // ask user 
  
   IList <Element> ps = uidoc.Selection.PickElementsByRectangle();
   Transaction t = new Transaction(doc,"Set offset");
    
             t.Start();
   foreach (Element e in ps) 
   {
   
    
    if (e.Category.Name == "Pipes")
    {
    
    
             double psodia = e.LookupParameter("Outside Diameter").AsDouble();
             double hi =(h + (psodia/2));
             e.LookupParameter("Offset").Set(hi);
    
       }
    }
    t.Commit();
    
    }
 
  private void InternalStartup()
  {
   this.Startup += new System.EventHandler(Module_Startup);
   this.Shutdown += new System.EventHandler(Module_Shutdown);
  }
  #endregion
 }
}

Hope you find it useful, let me know your comments!