WPF pass event method to viewmodel via Interaction:CallMethodAction,TargetObject MethodName

<Window x:Class="WpfApp71.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:WpfApp71"
        mc:Ignorable="d"
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:interaction="http://schemas.microsoft.com/expression/2010/interactions"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <DataGrid x:Name="dg" Grid.Row="1" ItemsSource="{Binding BooksCollection,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" 
VerticalAlignment="Stretch" HorizontalAlignment="Stretch" BorderBrush="Blue"
 BorderThickness="3" SelectionMode="Extended"
SelectedItem="{Binding SelectedBook,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" >
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="SelectionChanged">
                    <interaction:CallMethodAction TargetObject="{Binding}" MethodName="OnSelectionChanged"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </DataGrid>
    </Grid>
</Window>



//cs
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
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.Navigation;
using System.Windows.Shapes;

namespace WpfApp71
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            MainVM vm = new MainVM();
            this.DataContext = vm;
        }
    }

    public class Book
    {
        public int Id { get; set; }
        public string ISBN { get; set; }
        public string Name { get; set; }
        public string Summary { get; set; }
        public string Title { get; set; }
        public string Topic { get; set; }
    }

    public class ModelBase : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged(string propName)
        {
            var handler = PropertyChanged;
            if (handler != null)
            {
                handler?.Invoke(this, new PropertyChangedEventArgs(propName));
            }
        }
    }

    public class MainVM:ModelBase
    {
        public MainVM()
        {
            InitLV();
        }
        private void InitLV()
        {
            BooksCollection = new ObservableCollection<Book>();
            for (int i = 0; i < 1000; i++)
            {
                BooksCollection.Add(new Book()
                {
                    Id = i + 1,
                    ISBN = $"ISBN_{i + 1}",
                    Name = $"Name_{i + 1}",
                    Summary = $"Summary{i + 1}",
                    Title = $"Title_{i + 1}",
                    Topic = $"Topic{i + 1}",
                });
            }
        }

        private ObservableCollection<Book> booksCollection;
        public ObservableCollection<Book> BooksCollection
        {
            get
            {
                return booksCollection;
            }
            set
            {
                if (value != booksCollection)
                {
                    booksCollection = value;
                }
            }
        } 

        public void OnSelectionChanged(object sender,SelectionChangedEventArgs e)
        {
            var dg = sender as DataGrid;
            var selectedItems = e.AddedItems;
            StringBuilder builder = new StringBuilder();
            foreach(var item in selectedItems) 
            {
                var bk= item as Book;
                if(bk!=null)
                {
                    builder.AppendLine($"Id:{bk.Id},Name:{bk.Name}");
                } 
            }

            System.Windows.MessageBox.Show($"{builder.ToString()}", $"Selected {selectedItems.Count} items", MessageBoxButton.OK);
        }
    }

}

Key part

1.Install System.Windows.Interactivity.WPF from nuget;

2.Add interactivity and interactivity in xaml

3.Pass event method to viewmodel via interaction:CallMethodAction and specified MethodName

 <i:Interaction.Triggers>
     <i:EventTrigger EventName="SelectionChanged">
         <interaction:CallMethodAction TargetObject="{Binding}" MethodName="OnSelectionChanged"/>
     </i:EventTrigger>
 </i:Interaction.Triggers>

4.Implemented the MethodName in viewmodel with same signature as event method in xaml.cs

 public void OnSelectionChanged(object sender,SelectionChangedEventArgs e)

Be cautious,the Method's accessor must be public