CODE EXAMPLE FOR CSHARP

datagrid drop file wpf mvvm example

public class DropFilesBehaviorExtension
{
    public static readonly DependencyProperty IsEnabledProperty = DependencyProperty.RegisterAttached(
        "IsEnabled", typeof(bool), typeof(DropFilesBehaviorExtension), new FrameworkPropertyMetadata(default(bool), OnPropChanged)
        {
            BindsTwoWayByDefault = false,
        });

    private static void OnPropChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (!(d is FrameworkElement fe))
            throw new InvalidOperationException();
        if ((bool)e.NewValue)
        {
            fe.AllowDrop = true;
            fe.Drop += OnDrop;
            fe.PreviewDragOver += OnPreviewDragOver;
        }
        else
        {
            fe.AllowDrop = false;
            fe.Drop -= OnDrop;
            fe.PreviewDragOver -= OnPreviewDragOver;
        }
    }

    private static void OnPreviewDragOver(object sender, DragEventArgs e)
    {
        // NOTE: PreviewDragOver subscription is required at least when FrameworkElement is a TextBox
        // because it appears that TextBox by default prevent Drag on preview...
        e.Effects = DragDropEffects.Move;
        e.Handled = true;
    }

    private static void OnDrop(object sender, DragEventArgs e)
    {
        var dataContext = ((FrameworkElement)sender).DataContext;
        if (!(dataContext is IFilesDropped filesDropped))
        {
            if (dataContext != null)
                Trace.TraceError($"Binding error, '{dataContext.GetType().Name}' doesn't implement '{nameof(IFilesDropped)}'.");
            return;
        }

        if (!e.Data.GetDataPresent(DataFormats.FileDrop))
            return;

        if (e.Data.GetData(DataFormats.FileDrop) is string[] files)
            filesDropped.OnFilesDropped(files);
    }

    public static void SetIsEnabled(DependencyObject element, bool value)
    {
        element.SetValue(IsEnabledProperty, value);
    }

    public static bool GetIsEnabled(DependencyObject element)
    {
        return (bool)element.GetValue(IsEnabledProperty);
    }
}