Defining the model

Our model class is going to be fairly small. Its main purpose will be to encapsulate calls to the bootstrapper so as to present a simplified API to the viewmodel. Add a new C# class file to the Models folder and name it BootstrapperApplicationModel. Update it with the following code:

using Microsoft.Tools.WindowsInstallerXml.Bootstrapper;
using System;
using System.Windows;
using System.Windows.Interop;

namespace CustomBA.Models
{
    public class BootstrapperApplicationModel
    {
        private IntPtr hwnd;
        
        public BootstrapperApplicationModel(
          BootstrapperApplication bootstrapperApplication)
        {
            this.BootstrapperApplication =  
              bootstrapperApplication;
            this.hwnd = IntPtr.Zero;
        }

        public BootstrapperApplication BootstrapperApplication { get; private set; }

        public int FinalResult { get; set; }

        public void SetWindowHandle(Window view)
        {
            this.hwnd...