dockableviewmode.cs

class DockableViewModel : ViewModelBase
	{
		
		public DockableViewModel(UIControlledApplication a)
		{
            a.ViewActivated += OnViewActivated;
		}

		private void OnViewActivated(object sender, ViewActivatedEventArgs e)
		{
			this.Document = e.Document;
        }

		private Document document;
		public Document Document
		{
			get => document;
            set
			{
				document = value;
				OnPropertyChanged("Document");
			}
		}

	}