Create new Pipe using Pipe.Create

#region Namespaces
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Windows.Forms.VisualStyles;
using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.DB.Plumbing;
using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
#endregion

namespace PipeCreate
{
    [Transaction(TransactionMode.Manual)]
    public class Command : IExternalCommand
    {
        public Result Execute(
          ExternalCommandData commandData,
          ref string message,
          ElementSet elements)
        {
            UIApplication uiapp = commandData.Application;
            UIDocument uidoc = uiapp.ActiveUIDocument;
            Application app = uiapp.Application;
            Document doc = uidoc.Document;

            // Extract all pipe system types
            var mepSystemTypes
              = new FilteredElementCollector(doc)
                //.WhereElementIsNotElementType()
                .OfClass(typeof(PipingSystemType))
                .OfType<PipingSystemType>()
                .ToList();

            // get the Domestic hot water type
            var domesticHotWaterSystemType =
                mepSystemTypes
                    .FirstOrDefault(st => st.SystemClassification == MEPSystemClassification.DomesticHotWater);

            if (domesticHotWaterSystemType == null)
            {
                message = "Could not found Domestic Hot Water System Type";
                return Result.Failed;
            }

            // looking for the PipeType
            var pipeTypes =
                new FilteredElementCollector(doc)
                    .OfClass(typeof (PipeType))
                    .OfType<PipeType>()
                    .ToList();

            // get the first type from the collection
            var firstPipeType =
                pipeTypes.FirstOrDefault();

            if (firstPipeType == null)
            {
                message = "Could not found Pipe Type";
                return Result.Failed;
            }


            var level = uidoc.ActiveView.GenLevel;

            if (level == null)
            {
                message = "Wrong Active View";
                return Result.Failed;
            }


            var startPoint = XYZ.Zero;

            var endPoint = new XYZ(100, 0, 0);

            using (var t = new Transaction(doc, "Create pipe using Pipe.Create"))
            {
                t.Start();
                var pipe = Pipe.Create(doc,
                    domesticHotWaterSystemType.Id,
                    firstPipeType.Id,
                    level.Id,
                    startPoint,
                    endPoint);

                t.Commit();
            }

            return Result.Succeeded;
        }
    }
}