WPF pass MainWindow to viewmodel as a shortcut for viewmodel

 public partial class MainWindow : Window
 {
     public MainWindow()
     {
         InitializeComponent();
         var vm = new MainVM(this);
         this.DataContext = vm;
     }
 }

 public class MainVM : INotifyPropertyChanged
 {
     private MainWindow mainWin;
     public MainVM(MainWindow win)
     {
         mainWin = win;
         if (mainWin != null)
         {
             MainVMLoaded();
         }
     }
}

 

 

 

//xaml
<Window x:Class="WpfApp262.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp262"
        mc:Ignorable="d" WindowState="Maximized"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Image x:Name="img" Source="{Binding ImgUrl,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
            <Image.RenderTransform>
                <TransformGroup>
                    <ScaleTransform x:Name="scaler" x:FieldModifier="public"/>
                </TransformGroup>
            </Image.RenderTransform>
        </Image>
        <Button x:Name="upBtn" Content="Former" HorizontalAlignment="Left" VerticalAlignment="Bottom" Width="100" Height="50"/>
        <Button x:Name="nextBtn" Content="Next" HorizontalAlignment="Right" VerticalAlignment="Bottom" Width="100" Height="50"/>
    </Grid>
</Window>


//cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Media.TextFormatting;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp262
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            var vm = new MainVM(this);
            this.DataContext = vm;
        }
    }

    public class MainVM : INotifyPropertyChanged
    {
        private MainWindow mainWin;
        public MainVM(MainWindow win)
        {
            mainWin = win;
            if (mainWin != null)
            {
                MainVMLoaded();
            }
        }

        private void MainVMLoaded()
        {
            mainWin.MouseWheel += MainWin_MouseWheel;
            if (mainWin.upBtn != null)
            {
                mainWin.upBtn.Click += UpBtn_Click;
            }
            if (mainWin.nextBtn != null)
            {
                mainWin.nextBtn.Click += NextBtn_Click;
            }

            imgsList = new List<string>(System.IO.Directory.GetFiles(@"../../Images"));
            if (imgsList != null && imgsList.Any())
            {
                ImgUrl = imgsList[0];
            }
        }

        private void NextBtn_Click(object sender, RoutedEventArgs e)
        {
            if (++imgIdx >= imgsList.Count)
            {
                imgIdx = 0;
            }
            ImgUrl = imgsList[imgIdx];
        }

        private void UpBtn_Click(object sender, RoutedEventArgs e)
        {
            if(--imgIdx<0)
            {
                imgIdx = imgsList.Count - 1;
            }
            ImgUrl= imgsList[imgIdx];
        }

        private void MainWin_MouseWheel(object sender, MouseWheelEventArgs e)
        {
            if (mainWin.scaler != null)
            {
                if (e.Delta > 0)
                {
                    mainWin.scaler.ScaleX *= 1.2;
                    mainWin.scaler.ScaleY *= 1.2;
                }
                else
                {
                    mainWin.scaler.ScaleX /= 1.2;
                    mainWin.scaler.ScaleY /= 1.2;
                }
                mainWin.scaler.CenterX = e.GetPosition(mainWin.img).X;
                mainWin.scaler.CenterY = e.GetPosition(mainWin.img).Y;
            }
        }

        
        private List<string> imgsList;
        private int imgIdx = 0;

        private string imgUrl;
        public string ImgUrl
        {
            get
            {
                return imgUrl;
            }
            set
            {
                if (imgUrl != value)
                {
                    imgUrl = value;
                    OnPropertyChanged(nameof(ImgUrl)); 
                    if(mainWin!=null)
                    {
                        mainWin.Title = ImgUrl;
                    }
                }
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged(string propertyName)
        {
            var handler = PropertyChanged;
            if (handler != null)
            {
                handler?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
}