WPF customize datagrid behavior based on behavior<datagrid> with command and command parameter

Install-Package Microsoft.Xaml.Behaviors.Wpf
Install-Package Newtonsoft.Json

 

public class DatagridBehavior : Behavior<DataGrid>
{
    ContextMenu ctxMenu;
    MenuItem saveJsonMenuItem;
    MenuItem deleteMenuItem;


    public ICommand SaveJsonCommand
    {
        get { return (ICommand)GetValue(SaveJsonCommandProperty); }
        set { SetValue(SaveJsonCommandProperty, value); }
    }

    // Using a DependencyProperty as the backing store for SaveJsonCommand.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty SaveJsonCommandProperty =
        DependencyProperty.Register(nameof(SaveJsonCommand), typeof(ICommand),
            typeof(DatagridBehavior), new PropertyMetadata(null));





    public ICommand DeleteCommand
    {
        get { return (ICommand)GetValue(DeleteCommandProperty); }
        set { SetValue(DeleteCommandProperty, value); }
    }

    // Using a DependencyProperty as the backing store for DeleteCommand.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty DeleteCommandProperty =
        DependencyProperty.Register(nameof(DeleteCommand), typeof(ICommand),
            typeof(DatagridBehavior), new PropertyMetadata(null));





    public object CmdPara
    {
        get { return (object)GetValue(CmdParaProperty); }
        set { SetValue(CmdParaProperty, value); }
    }

    // Using a DependencyProperty as the backing store for CmdPara.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty CmdParaProperty =
        DependencyProperty.Register(nameof(CmdPara), typeof(object),
            typeof(DatagridBehavior), new PropertyMetadata(null));



    public DatagridBehavior()
    {
        
    }

    protected override void OnAttached()
    {
        CreateContextMenu();
        AssociatedObject.ContextMenu = ctxMenu;
        base.OnAttached();
    }

    private void CreateContextMenu()
    {
        ctxMenu = new ContextMenu();
        saveJsonMenuItem = new MenuItem()
        {
            Header = "Save Json"
        };
        saveJsonMenuItem.Click += SaveJsonMenuItem_Click;
        ctxMenu.Items.Add(saveJsonMenuItem);

        deleteMenuItem = new MenuItem()
        {
            Header = "Delete Item"
        };
        deleteMenuItem.Click += DeleteMenuItem_Click;
        ctxMenu.Items.Add(deleteMenuItem);
    }

    private void DeleteMenuItem_Click(object sender, RoutedEventArgs e)
    {
        DeleteCommand?.Execute(CmdPara);
    }

    private void SaveJsonMenuItem_Click(object sender, RoutedEventArgs e)
    {
        SaveJsonCommand?.Execute(CmdPara);
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
    }
}

  <behavior:Interaction.Behaviors>
      <local:DatagridBehavior
    SaveJsonCommand="{Binding Path=DataContext.SaveCmd,RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
    DeleteCommand="{Binding Path=DataContext.DeleteCmd,RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
    CmdPara="{Binding Path=SelectedItems, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
  </behavior:Interaction.Behaviors>    




public ICommand SelectedCmd { get; set; }
public ICommand SaveCmd { get; set; }
public ICommand DeleteCmd { get; set; }

 private void InitCmds()
 {
     SelectedCmd = new DelCommand(SelectedCmdExecuted);
     SaveCmd = new DelCommand(SaveCmdExecuted);
     DeleteCmd = new DelCommand(DeleteCmdExecuted);
 }

 private void DeleteCmdExecuted(object? obj)
 {
     var items = ((System.Collections.IList)obj).Cast<Book>()?.ToList();
     if(items!=null && items.Any())
     {
         foreach(var item in items)
         {
             if(BooksCollection.Remove(item))
             {
                 System.Diagnostics.Debug.WriteLine($"{DateTime.Now}: removed {item}");
             }                    
         }
     }
 }

 private void SaveCmdExecuted(object? obj)
 {
     var items = ((System.Collections.IList)obj).Cast<Book>()?.ToList();
     if(items!=null && items.Any())
     {
         string jsonStr = JsonConvert.SerializeObject(items, Formatting.Indented);
         string jsonFile = $"Json_{DateTime.Now.ToString("yyyyMMddHHmmssffff")}.json";
         using (StreamWriter jsonWriter = new StreamWriter(jsonFile,false, Encoding.UTF8))
         {
             jsonWriter.WriteLine(jsonStr);
             System.Diagnostics.Debug.WriteLine($"{DateTime.Now},write json to {jsonFile}");
         }
     }
 }

2026-05-19 18:42:00,write json to Json_202605191842003493.json
Selected count:14,First Id:1,Last Id:14
Selected count:1,First Id:11,Last Id:11
Selected count:5,First Id:11,Last Id:15
Selected count:5,First Id:11,Last Id:15
2026-05-19 18:42:09: removed Id:11,Name:Name_11,ISBN:ISBN_11_12352a8065fd439bbd32d45fceaabbc4
2026-05-19 18:42:09: removed Id:12,Name:Name_12,ISBN:ISBN_12_e0859de5557844679935fd870e3ad33f
2026-05-19 18:42:09: removed Id:13,Name:Name_13,ISBN:ISBN_13_a21f1e5c264d43e5bda089d8ecc040ce
2026-05-19 18:42:09: removed Id:14,Name:Name_14,ISBN:ISBN_14_dd7476cee61740fba7190b022fb84cb7
2026-05-19 18:42:09: removed Id:15,Name:Name_15,ISBN:ISBN_15_3cd20b8d7e27447a8901b3e2ece17439

 

 

<Window x:Class="WpfApp31.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:WpfApp31"
        xmlns:behavior="http://schemas.microsoft.com/xaml/behaviors"
        mc:Ignorable="d"
        Title="{Binding MainTitle}" WindowState="Maximized">
    <Window.DataContext>
        <local:MainVM/>
    </Window.DataContext>
    <Grid>
        <DataGrid ItemsSource="{Binding BooksCollection}"
                  VirtualizingPanel.IsVirtualizing="True"
                  VirtualizingPanel.VirtualizationMode="Recycling"
                  VirtualizingPanel.CacheLengthUnit="Item"
                  VirtualizingPanel.CacheLength="2,2"
                  ScrollViewer.CanContentScroll="True"
                  ScrollViewer.IsDeferredScrollingEnabled="True"
                  UseLayoutRounding="True"
                  SnapsToDevicePixels="True"
                  EnableColumnVirtualization="True"
                  EnableRowVirtualization="True"
                  AutoGenerateColumns="True"
                  CanUserAddRows="False"
                  SelectionMode="Extended"
                  IsReadOnly="True">
            <DataGrid.Resources>
                <Style TargetType="DataGridRow">
                    <Setter Property="FontSize" Value="30"/>
                    <Style.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="FontSize" Value="50"/>
                            <Setter Property="Foreground" Value="Red"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </DataGrid.Resources>
            <behavior:Interaction.Triggers>
                <behavior:EventTrigger EventName="MouseUp">
                    <behavior:InvokeCommandAction 
                        Command="{Binding SelectedCmd}"
                        PassEventArgsToCommand="True"
                        CommandParameter="{Binding Path=SelectedItems,RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}">
                    </behavior:InvokeCommandAction>
                </behavior:EventTrigger>
                <behavior:EventTrigger EventName="MouseDoubleClick">
                    <behavior:CallMethodAction
                        MethodName="DataGrid_MouseDoubleClick"
                        TargetObject="{Binding}"/>
                </behavior:EventTrigger>
            </behavior:Interaction.Triggers>
            <behavior:Interaction.Behaviors>
                <local:DatagridBehavior
              SaveJsonCommand="{Binding Path=DataContext.SaveCmd,RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
              DeleteCommand="{Binding Path=DataContext.DeleteCmd,RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
              CmdPara="{Binding Path=SelectedItems, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
            </behavior:Interaction.Behaviors>            
        </DataGrid>
    </Grid>
</Window>

using Microsoft.Xaml.Behaviors;
using Newtonsoft.Json;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Diagnostics.Eventing.Reader;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
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;
using System.Windows.Threading;

namespace WpfApp31
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        } 
    }

    public class MainVM : INotifyPropertyChanged
    {
        private DispatcherTimer tmr;
        private static long idx = 0;
        public ICommand SelectedCmd { get; set; }
        public ICommand SaveCmd { get; set; }
        public ICommand DeleteCmd { get; set; }
        public MainVM()
        {
            if (!DesignerProperties.GetIsInDesignMode(new DependencyObject()))
            {
                Task.Run(async () =>
                {
                    await InitBooksCollectionAsync();
                });
            } 

            InitCmds(); 
        }

        private void InitCmds()
        {
            SelectedCmd = new DelCommand(SelectedCmdExecuted);
            SaveCmd = new DelCommand(SaveCmdExecuted);
            DeleteCmd = new DelCommand(DeleteCmdExecuted);
        }

        private void DeleteCmdExecuted(object? obj)
        {
            var items = ((System.Collections.IList)obj).Cast<Book>()?.ToList();
            if(items!=null && items.Any())
            {
                foreach(var item in items)
                {
                    if(BooksCollection.Remove(item))
                    {
                        System.Diagnostics.Debug.WriteLine($"{DateTime.Now}: removed {item}");
                    }                    
                }
            }
        }

        private void SaveCmdExecuted(object? obj)
        {
            var items = ((System.Collections.IList)obj).Cast<Book>()?.ToList();
            if(items!=null && items.Any())
            {
                string jsonStr = JsonConvert.SerializeObject(items, Formatting.Indented);
                string jsonFile = $"Json_{DateTime.Now.ToString("yyyyMMddHHmmssffff")}.json";
                using (StreamWriter jsonWriter = new StreamWriter(jsonFile,false, Encoding.UTF8))
                {
                    jsonWriter.WriteLine(jsonStr);
                    System.Diagnostics.Debug.WriteLine($"{DateTime.Now},write json to {jsonFile}");
                }
            }
        }


        public void DataGrid_MouseDoubleClick(object sender, MouseButtonEventArgs e)
        {
            var dg = sender as DataGrid;
            if (dg != null)
            {
                var items = dg.SelectedItems.Cast<Book>().ToList();
                var msg = $"Selected {items.Count} items.FirstId:{items.FirstOrDefault()?.Id},LastId:{items.LastOrDefault()?.Id}";
                System.Diagnostics.Debug.WriteLine(msg);
            }
        }

        private void SelectedCmdExecuted(object? obj)
        {
            var selectedItems = ((System.Collections.IList)obj)?.Cast<Book>();
            var msg = $"Selected count:{selectedItems.Count()},First Id:{selectedItems.FirstOrDefault()?.Id},Last Id:{selectedItems.LastOrDefault()?.Id}";
            System.Diagnostics.Debug.WriteLine(msg);
        }

        private static long GetIncrementIdx()
        {
            return Interlocked.Increment(ref idx);
        }

        private async Task InitBooksCollectionAsync(int cnt = 1000000)
        {
            BooksCollection = new ObservableCollection<Book>();
            List<Book> booksList = new List<Book>();
            for (int i = 0; i < cnt; i++)
            {
                var a = GetIncrementIdx();
                booksList.Add(new Book()
                {
                    Id = a,
                    Name = $"Name_{a}",
                    Author = $"Author_{a}",
                    Abstract = $"Abstract_{a}",
                    ISBN = $"ISBN_{a}_{Guid.NewGuid():N}",
                    Comment = $"Comment_{a}",
                    Content = $"Content_{a}",
                    Summary = $"Summary_{a}",
                    Title = $"Title_{a}",
                    Topic = $"Topic_{a}"
                });

                if (i % 100000 == 0)
                {
                    await PopulateAsync(booksList);
                }
            }

            if (booksList.Any())
            {
                await PopulateAsync(booksList);
            }
        }

        private async Task PopulateAsync(List<Book> booksList)
        {
            var tempList = booksList.ToList();
            booksList.Clear();
            await Application.Current.Dispatcher.InvokeAsync(() =>
            {
                foreach (var bk in tempList)
                {
                    BooksCollection.Add(bk);
                }
                MainTitle = $"{DateTime.Now},loaded {BooksCollection.Count} items";
            }, DispatcherPriority.Background);
        }


        private IList<Book> selectedBooks;
        public IList<Book> SelectedBooks
        {
            get
            {
                return selectedBooks;
            }
            set
            {
                if (value != selectedBooks)
                {
                    selectedBooks = value;
                    OnPropertyChanged();
                }
            }
        }

        private string mainTitle = $"{DateTime.Now},loading...";
        public string MainTitle
        {
            get
            {
                return mainTitle;
            }
            set
            {
                if (value != mainTitle)
                {
                    mainTitle = value;
                    OnPropertyChanged();
                }
            }
        }

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

        public event PropertyChangedEventHandler? PropertyChanged;
        private void OnPropertyChanged([CallerMemberName] string propName = "")
        {
            var handler = PropertyChanged;
            handler?.Invoke(this, new PropertyChangedEventArgs(propName));
        }
    }

    public class DelCommand : ICommand
    {
        private Action<object?>? execute;
        private Predicate<object?>? canExecute;
        public DelCommand(Action<object?>? executeValue, Predicate<object?>? canExecuteValue = null)
        {
            execute = executeValue ?? throw new ArgumentNullException(nameof(executeValue));
            canExecute = canExecuteValue;
        }


        public event EventHandler? CanExecuteChanged
        {
            add
            {
                CommandManager.RequerySuggested += value;
            }
            remove
            {
                CommandManager.RequerySuggested -= value;
            }
        }

        public bool CanExecute(object? parameter)
        {
            return canExecute == null ? true : canExecute(parameter);
        }

        public void Execute(object? parameter)
        {
            execute?.Invoke(parameter);
        }
    }

    public class Book
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public string Author { get; set; }
        public string Abstract { get; set; }
        public string ISBN { get; set; }
        public string Comment { get; set; }
        public string Content { get; set; }
        public string Summary { get; set; }
        public string Title { get; set; }
        public string Topic { get; set; }

        public override string ToString()
        {
            return $"Id:{Id},Name:{Name},ISBN:{ISBN}";
        }
    }

    public class DatagridBehavior : Behavior<DataGrid>
    {
        ContextMenu ctxMenu;
        MenuItem saveJsonMenuItem;
        MenuItem deleteMenuItem;


        public ICommand SaveJsonCommand
        {
            get { return (ICommand)GetValue(SaveJsonCommandProperty); }
            set { SetValue(SaveJsonCommandProperty, value); }
        }

        // Using a DependencyProperty as the backing store for SaveJsonCommand.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SaveJsonCommandProperty =
            DependencyProperty.Register(nameof(SaveJsonCommand), typeof(ICommand),
                typeof(DatagridBehavior), new PropertyMetadata(null));





        public ICommand DeleteCommand
        {
            get { return (ICommand)GetValue(DeleteCommandProperty); }
            set { SetValue(DeleteCommandProperty, value); }
        }

        // Using a DependencyProperty as the backing store for DeleteCommand.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty DeleteCommandProperty =
            DependencyProperty.Register(nameof(DeleteCommand), typeof(ICommand),
                typeof(DatagridBehavior), new PropertyMetadata(null));





        public object CmdPara
        {
            get { return (object)GetValue(CmdParaProperty); }
            set { SetValue(CmdParaProperty, value); }
        }

        // Using a DependencyProperty as the backing store for CmdPara.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty CmdParaProperty =
            DependencyProperty.Register(nameof(CmdPara), typeof(object),
                typeof(DatagridBehavior), new PropertyMetadata(null));



        public DatagridBehavior()
        {
            
        }

        protected override void OnAttached()
        {
            CreateContextMenu();
            AssociatedObject.ContextMenu = ctxMenu;
            base.OnAttached();
        }

        private void CreateContextMenu()
        {
            ctxMenu = new ContextMenu();
            saveJsonMenuItem = new MenuItem()
            {
                Header = "Save Json"
            };
            saveJsonMenuItem.Click += SaveJsonMenuItem_Click;
            ctxMenu.Items.Add(saveJsonMenuItem);

            deleteMenuItem = new MenuItem()
            {
                Header = "Delete Item"
            };
            deleteMenuItem.Click += DeleteMenuItem_Click;
            ctxMenu.Items.Add(deleteMenuItem);
        }

        private void DeleteMenuItem_Click(object sender, RoutedEventArgs e)
        {
            DeleteCommand?.Execute(CmdPara);
        }

        private void SaveJsonMenuItem_Click(object sender, RoutedEventArgs e)
        {
            SaveJsonCommand?.Execute(CmdPara);
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();
        }
    }
}

 

 

 

 

 

2026-05-19 18:50:27: removed Id:392835,Name:Name_392835,ISBN:ISBN_392835_98844b65f6164770b986a011953f094f
2026-05-19 18:50:27: removed Id:392836,Name:Name_392836,ISBN:ISBN_392836_6e4ae22266c649979abae5e2f2aaa596
2026-05-19 18:50:27: removed Id:392837,Name:Name_392837,ISBN:ISBN_392837_0e577274c5704ffca4b482c1f0f19182
2026-05-19 18:50:27: removed Id:392838,Name:Name_392838,ISBN:ISBN_392838_9164c28643c44982b223c922960c6e7d
2026-05-19 18:50:27: removed Id:392839,Name:Name_392839,ISBN:ISBN_392839_b962b2fba23d44debffe3741cd349c33
2026-05-19 18:50:27: removed Id:392840,Name:Name_392840,ISBN:ISBN_392840_93ffaf1bea4a4f24a029ae8631efb465
2026-05-19 18:50:27: removed Id:392841,Name:Name_392841,ISBN:ISBN_392841_2a600c9a5f8d4f2b8dd1055039a033dc