public void AddNewType(ClassViewModel type)
 {
     if (!this.Types.Contains(type))
         this.Types.Add(type);
 }
		/// <summary>
		/// Adds new (dropped) item to diagram.
		/// </summary>
		/// <param name="classViewModel">The model (representing a type) to be added.</param>
		/// <param name="point">The position.</param>
		/// <param name="offset">The displacement.</param>
		private void AddNewItemToDiagram(ClassViewModel classViewModel, Point point, ref int offset)
		{
			if (this.DataContext == null || !(this.DataContext is MainViewModel)) return;
			classViewModel.Position = new Point(point.X + ((offset % 5) * 200), point.Y + ((offset / 5) * 200));
			(this.DataContext as MainViewModel).ClassDiagramGraphSource.AddItem(classViewModel);
			offset++;
		}