Elements disappear after closing the form

Hello Revit gurus,

I am new to C# programming and for the past 2 days I couldn't find the solution for my problem. I have created an External addin that add tags to family instances based on its BuiltinCategory. The addin works as it should without any problems. However when I decided to create a form to expand the functionality of the addin that is when the headaches started.

I cut down my program into 3 parts. The first implements the ExternalCommandData method to show the form.

using System;
using System.Windows.Forms;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.DB.Plumbing;
using Autodesk.Revit.UI;
using Autodesk.Revit.DB.Architecture;
using Autodesk.Revit.UI.Selection;

namespace Pipes_Annotations1
{
    
    [Autodesk.Revit.Attributes.Transaction(Autodesk.Revit.Attributes.TransactionMode.Manual)]
    [Autodesk.Revit.Attributes.Journaling(Autodesk.Revit.Attributes.JournalingMode.NoCommandData)]

    public class pipesannotation1 : IExternalCommand
    {        
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            //tagging tagginng1 = new tagging(commandData);
            try
            {
                tagging m_tagging = new tagging();
                // show UI
                using (Form1 displayForm = new Form1(m_tagging,commandData))
                {
                    DialogResult result = displayForm.ShowDialog();
                    if (DialogResult.OK != result)
                    {
                        return Autodesk.Revit.UI.Result.Cancelled;
                    }
                }

                return Autodesk.Revit.UI.Result.Succeeded;
            }
            catch (Exception e)
            {
                message = e.Message;
                return Autodesk.Revit.UI.Result.Failed;
            }
        }
        

    }   
}

The Second Part creates the tags:

namespace Pipes_Annotations1
{
    public class tagging
    {        
        public FamilySymbol elemtag1 = null;
        public FamilySymbol elemtag2 = null;        
        public void tagging1(ExternalCommandData commandData)
        {
            MessageBox.Show("Started the program");
            try
            {                
                // Get the active document and view
                UIDocument revitDoc = commandData.Application.ActiveUIDocument;
                Autodesk.Revit.DB.View view = revitDoc.Document.ActiveView;
                StringBuilder message2 = new StringBuilder();
                FilteredElementCollector viewCollector = new FilteredElementCollector(revitDoc.Document, revitDoc.ActiveView.Id);
                viewCollector.OfCategory(BuiltInCategory.OST_PipeCurves);
                message2.AppendLine("Pipes category elements within active View: "
                   + viewCollector.ToElementIds().Count);

                FilteredElementCollector docCollector = new FilteredElementCollector(revitDoc.Document);
                docCollector.OfCategory(BuiltInCategory.OST_PipeCurves);
                message2.AppendLine("Pipes category elements within document: "
                   + docCollector.ToElementIds().Count);

                FilteredElementCollector Familytagcollector = new FilteredElementCollector(revitDoc.Document);
                Familytagcollector.OfCategory(BuiltInCategory.OST_PipeTags);
                Familytagcollector.OfClass(typeof(FamilySymbol));
                message2.AppendLine("Pipes tags category elements within document: "
                   + Familytagcollector.ToElementIds().Count);

                TaskDialog.Show("Revit", message2.ToString());                

                foreach (ElementId tagID in Familytagcollector.ToElementIds())
                {
                    FamilySymbol elemtag = revitDoc.Document.GetElement(tagID) as FamilySymbol;
                    Parameter elemtagfam = elemtag.get_Parameter(BuiltInParameter.ELEM_FAMILY_PARAM);                    
                    if (elemtag.Family.Name == "Pipe Size Tag")
                    {
                        elemtag1 = elemtag;
                        MessageBox.Show(elemtag.Family.Name);                        
                    }
                    else if (elemtag.Family.Name == "BOP")
                    {
                        elemtag2 = elemtag;                        
                        MessageBox.Show(elemtag.Family.Name);
                        
                    }
                }

                string message = "";
                if (viewCollector.ToElementIds().Count == 0)
                {
                    message = "No pipe selected!";
                    MessageBox.Show(message);                    
                }
                else
                {
                    foreach (ElementId elemId in viewCollector.ToElementIds())
                    {
                        message = " " + elemId;                        
                        Element elem = revitDoc.Document.GetElement(elemId);
                        if (elem.GetType() == typeof(Autodesk.Revit.DB.Plumbing.Pipe))
                        {                                                                                
                            Autodesk.Revit.DB.Plumbing.Pipe pipe = (Autodesk.Revit.DB.Plumbing.Pipe)elem;
                            LocationCurve pipelloc = pipe.Location as LocationCurve;
                            XYZ pipeStart = pipelloc.Curve.GetEndPoint(0);
                            XYZ pipeEnd = pipelloc.Curve.GetEndPoint(1);
                            XYZ pipeMid = pipelloc.Curve.Evaluate(0.5, true);                         

                            using (Transaction t = new Transaction(revitDoc.Document))
                            {
                                t.Start("Create new tag");                                
                                IndependentTag tag = revitDoc.Document.Create.NewTag(view, pipe, false,
                                    Autodesk.Revit.DB.TagMode.TM_ADDBY_CATEGORY,
                                    Autodesk.Revit.DB.TagOrientation.Horizontal, pipeMid );
                                tag.ChangeTypeId(elemtag1.Id);
                                                           
                                t.Commit();
                            }
                        }
                    }
                }
                
            }
            catch (Exception err)
            {
                string message = err.Message;
                //return Autodesk.Revit.UI.Result.Failed;
            }
        }
     }
}

The 3rd part is the form. In the form Structure under the button1_Click method, I added the tagging method only without ending this.Close();. The program works as it should and the tags are added. However, when I close the form manually, all my tags disappear. If I add this.Close(); after the tagging method, the program runs but none of the tags appear. So I am assuming that closing the form does not commit the transaction and whenever I close it all the tags disappear. I am not sure How to solve this issue and any help will be appreciated. the form code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.DB.Plumbing;
using Autodesk.Revit.UI;
using Autodesk.Revit.DB.Architecture;
using Autodesk.Revit.UI.Selection;
namespace Pipes_Annotations1
{

    //[TransactionAttribute(TransactionMode.Manual)]
    //[RegenerationAttribute(RegenerationOption.Manual)]

    public partial class Form1 : System.Windows.Forms.Form
    {
        private tagging m_tagging1;        
        ExternalCommandData commandData;
        public Form1(tagging m_tagging, ExternalCommandData commandData1)
        {
            m_tagging1 = m_tagging;
            commandData =  commandData1;                      
            InitializeComponent();
            
        }
        

        private void button1_Click(object sender, EventArgs e)
        {
            m_tagging1.tagging1(commandData);
        }

        
        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {            
            //System.Windows.Forms.Application.Exit();
        }

        private void groupBox1_Enter(object sender, EventArgs e)
        {

        }
    }
}

Thank you so much

Nayer Girgis