I’ve been struggling with the SelectionService implementation for a while already. I found out that MSDN2 docs were missing the obsolete part of half of the SelectionTypes enum members. For the purpose of testing I replaced the M$’s default implementation in the DesignSurface with my own (ISelectionService is one of the replaceable services in the DesignSurface service container). The results were scary… Seems like the M$ implementation is doing either hardcoding crap or just pure magic. From the few tests made it doesn’t take advantage of the SelectionTypes enum at all. After a few days hacking on the service I gave up on coding a M$ DesignSurface compatible SelectionService. Infact I feel like I’ve wasted my time on that one – I don’t need a M$ DesignSurface compatible SelectionService. Here you go with the actual SelectionService source code. (it’s not final version of course )

//
// System.ComponentModel.Design.SelectionService
//
// Authors:
//		Ivan N. Zlatev (contact i-nZ.net)
//
// (C) 2006 Ivan N. Zlatev

//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#if NET_2_0

using System;
using System.Collections;
using System.ComponentModel.Design;
using System.Windows.Forms;

namespace System.ComponentModel.Design
{

	internal class SelectionService : ISelectionService
	{

		private ArrayList _selection;
		private IServiceProvider _serviceProvider;
		private IComponent _primarySelection;

		public event EventHandler SelectionChanging;
		public event EventHandler SelectionChanged;

		public SelectionService (IServiceProvider serviceProvider)
		{
			_selection = new ArrayList();
			_serviceProvider = serviceProvider;
		}

		public ICollection GetSelectedComponents()
		{
			return _selection.ToArray ();
		}

		protected virtual void OnSelectionChanging ()
		{
			if (SelectionChanging != null) {
				SelectionChanging (this, EventArgs.Empty);
			}
		}

		protected virtual void OnSelectionChanged ()
		{
			if (SelectionChanged != null) {
				SelectionChanged (this, EventArgs.Empty);
			}
		}

		public object PrimarySelection
		{
			get { return _primarySelection; }
		}

		public int SelectionCount
		{
			get { return _selection.Count; }
		}

		private IComponent _RootComponent
		{
			get {
				if (_serviceProvider != null) {
					IDesignerHost designerHost = _serviceProvider.GetService (typeof (IDesignerHost)) as IDesignerHost;
					if (designerHost != null) {
						return designerHost.RootComponent;
					}
				}
				throw new InvalidOperationException ("No RootComponent");
			}
		}

		public bool GetComponentSelected (object component)
		{
			return _selection.Contains (component);
		}

		public void SetSelectedComponents (ICollection components)
 		{
			SetSelectedComponents (components, SelectionTypes.Auto);
		}

		// If the array is a null reference or does not contain any components,
		// SetSelectedComponents selects the top-level component in the designer.
		//
		public void SetSelectedComponents (ICollection components, SelectionTypes selectionType)
		{
			bool primary, add, remove, replace, toggle, auto;
			primary = add = remove = replace = toggle = auto = false;

			OnSelectionChanging ();

			if (_selection == null) {
				throw new InvalidOperationException("_selection == null");
			}

			if (components == null || components.Count == 0) {
				components = new ArrayList ();
				((ArrayList) components).Add (_RootComponent);
				selectionType = SelectionTypes.Replace;
			}

			if (!Enum.IsDefined (typeof (SelectionTypes), selectionType)) {
				selectionType = SelectionTypes.Auto;
			}

			auto = ((selectionType & SelectionTypes.Auto) == SelectionTypes.Auto);

			if (auto) {
				toggle = (((Control.ModifierKeys & Keys.Control) == Keys.Control) || ((Control.ModifierKeys & Keys.Shift) == Keys.Shift));
				if (!toggle) {
					if (components.Count == 1) {
						primary = true;
					}
					else {
						replace = true;
					}
				}
			}
			else {
				primary = ((selectionType & SelectionTypes.Primary) == SelectionTypes.Primary);
				add = ((selectionType & SelectionTypes.Add) == SelectionTypes.Add);
				remove = ((selectionType & SelectionTypes.Remove) == SelectionTypes.Remove);
				replace = ((selectionType & SelectionTypes.Replace) == SelectionTypes.Replace);
				toggle = ((selectionType & SelectionTypes.Toggle) == SelectionTypes.Toggle);
			}

			if (replace) {
				_selection.Clear ();
				add = true;
			}

			if (add) {
				foreach (object component in components) {
					if (component is IComponent && !_selection.Contains (component)) {
						_selection.Add (component);
						_primarySelection = (IComponent) component;
					}
				}
			}

			if (remove) {
				foreach (object component in components) {
					if (component is IComponent && _selection.Contains (component)) {
						_selection.Remove (component);
						if (component == _primarySelection) {
							_primarySelection = _RootComponent;
						}
					}
				}
			}

			if (toggle) {
				foreach (object component in components) {
					if (component is IComponent) {
						if (_selection.Contains (component)) {
							_selection.Remove (component);
							if (component == _primarySelection) {
								_primarySelection = _RootComponent;
							}
						}
						else {
							_selection.Add (component);
							_primarySelection = (IComponent) component;
						}
					}
				}
			}

			if (primary) {
				object primarySelection = null;

				foreach (object component in components) {
					primarySelection = component;
					break;
				}

				if (_selection.Contains(primarySelection)) {
					_primarySelection = (IComponent) primarySelection;
				}
			}				

			OnSelectionChanged ();
		}

	}

}
#endif