✅ C# CS0246

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Autodesk.Revit.ApplicationServices;
using System.Windows.Forms;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.Attributes;

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

            var collector = new FilteredElementCollector(doc)
                .OfCategory(BuiltInCategory.OST_Walls);

            var simpleForm = new SimpleForm();
            simpleForm.ShowDialog();


            return Result.Succeeded;

        }
    }
}