wpfCore3.1 binding mouse event to mvvm

Question

is there a way to bind xaml control mouse event to mouse event handler in viewmodel?
i'm using wpf core3.1 MS VS2019.

Accepted Answer

Hi, without seeing your code I cannot reproduce your problems. Try following demo:

--------------------------------------

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Windows;  
using System.Windows.Controls;  
using System.Windows.Input;  
using System.Windows.Media.Media3D;  
  
namespace WpfApp03  
{  
  public class ViewModel  
  {  
  
    List ViewPorts = new List();  
  
    public static readonly DependencyProperty ReferenceProperty =  
      DependencyProperty.RegisterAttached("Reference", typeof(bool),  
                                          typeof(FrameworkElement),  
                                          new UIPropertyMetadata(false, OnReferenceChanged));  
    public static bool GetReference(DependencyObject obj) => (bool)obj.GetValue(ReferenceProperty);  
    public static void SetReference(DependencyObject obj, bool value) => obj.SetValue(ReferenceProperty, value);  
  
    private static void OnReferenceChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)  
    {  
      var vp = depObj as Viewport3D;  
      if (vp == null || !(e.NewValue is Boolean)) return;  
      var vm = vp.DataContext as ViewModel;  
      if (vm.ViewPorts.Count == 0 || vm.ViewPorts.Where((v) => v.VPort == vp).Count() == 0)  
        vm.ViewPorts.Add(new MyViewPort() { VPort = vp });  
    }  
  }  
  
  public class MyViewPort  
  {  
    private Viewport3D _vPort;  
    public Viewport3D VPort  
    {  
      get => this._vPort;  
      set  
      {  
        if (this._vPort == null)  
        {  
          this._vPort = value;  
          this._vPort.MouseDown += _vPort_MouseDown;  
          this._vPort.MouseMove += _vPort_MouseMove;  
          this._vPort.MouseUp += _vPort_MouseUp;  
          this._vPort.Loaded += _vPort_Loaded;  
        }  
      }  
    }  
  
    private AxisAngleRotation3D rot = new AxisAngleRotation3D(new Vector3D(0, 2, 0), 0);  
    private void _vPort_Loaded(object sender, RoutedEventArgs e)  
    {  
      var mod = this._vPort.Children[0] as ModelVisual3D;  
      mod.Transform = new RotateTransform3D(rot);  
    }  
  
    private Point pt = new Point(double.NaN, double.NaN);  
    private void _vPort_MouseDown(object sender, MouseButtonEventArgs e) =>       pt = e.GetPosition(this._vPort);  
    private void _vPort_MouseMove(object sender, MouseEventArgs e)  
    {  
      if (!double.IsNaN(pt.X))  
      {  
        Point pt1 = e.GetPosition(this._vPort);  
        double ang = pt1.X - pt.X;  
        rot.Angle = ang;  
      }  
    }  
    private void _vPort_MouseUp(object sender, MouseButtonEventArgs e)=>       pt = new Point(double.NaN, double.NaN);  
  }  
}

Answer

Hi, you can use "attached property" pattern like in following demo:

----------------------------------------------------------

using System;  
using System.Collections.ObjectModel;  
using System.Windows;  
  
namespace WpfApp02  
{  
  public class ViewModel   
  {  
    public ObservableCollection Log { get; set; } = new ObservableCollection();  
    public void InsertLogEntry(string msg) => Log.Insert(0, msg);  
  
    public static readonly DependencyProperty MouseEventsProperty =  
      DependencyProperty.RegisterAttached("MouseEvents", typeof(bool),  
                                          typeof(FrameworkElement),  
                                          new UIPropertyMetadata(false, OnMouseEventsChanged));  
    public static bool GetMouseEvents(DependencyObject obj) => (bool)obj.GetValue(MouseEventsProperty);  
    public static void SetMouseEvents(DependencyObject obj, bool value) => obj.SetValue(MouseEventsProperty, value);  
  
    private static void OnMouseEventsChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)  
    {  
      var fwe = depObj as FrameworkElement;  
      if (fwe == null || !(e.NewValue is Boolean)) return;  
      if ((bool)(e.NewValue)) fwe.MouseDown += OnMouseDown;  
      else fwe.MouseDown -= OnMouseDown;  
    }  
  
    private static void OnMouseDown(object sender, EventArgs e)  
    {  
      var uie = sender as FrameworkElement;  
      var vm = uie.DataContext as ViewModel;  
      vm.InsertLogEntry($"MouseDown: {DateTime.Now:HH:mm:ss.fff}");  
    }  
  }  
}

wpfCore3.1 binding mouse event to mvvm

1 additional answer