Add a designItembinding, this can be used when you create your own Property Editors, they should not only Bind

to the Value of the View, no they should also change the Properties of the underlaying DesignItem

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/MarkupExtensions/DesignItemBinding.cs

@@ -0,0 +1,151 @@
+// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
+// 
+// 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.
+
+using System;
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+using System.Windows.Markup;
+using ICSharpCode.WpfDesign.UIExtensions;
+
+[assembly: XmlnsDefinition("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "ICSharpCode.WpfDesign.Designer.MarkupExtensions")]
+
+
+namespace ICSharpCode.WpfDesign.Designer.MarkupExtensions
+{
+	/// <summary>
+	/// A Binding to a DesignItem of Object
+	/// 
+	/// This can be used for Example your own Property Pages for Designer Objects
+	/// </summary>
+	public class DesignItemBinding : MarkupExtension
+	{
+		private string _propertyName;
+		private Binding _binding;
+		private DesignItemSetConverter _converter;
+		private DependencyProperty _targetProperty;
+		private FrameworkElement _targetObject;
+
+		public bool SingleItemProperty { get; set; }
+		
+		public UpdateSourceTrigger UpdateSourceTrigger { get; set; }
+
+		public DesignItemBinding(string path)
+		{
+			this._propertyName = path;
+			
+			UpdateSourceTrigger = UpdateSourceTrigger.Default;
+		}
+
+		public override object ProvideValue(IServiceProvider serviceProvider)
+		{
+			IProvideValueTarget service = (IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget));
+			_targetObject = service.TargetObject as FrameworkElement;
+			_targetProperty = service.TargetProperty as DependencyProperty;
+			
+			_targetObject.DataContextChanged += targetObject_DataContextChanged;
+
+			return null;
+		}
+
+		void targetObject_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
+		{
+			var ctx = ((FrameworkElement) sender).DataContext as FrameworkElement;
+
+			var surface = ctx.TryFindParent<DesignSurface>();
+
+			if (surface != null)
+			{
+				_binding = new Binding(_propertyName);
+				_binding.Source = ctx;
+				_binding.UpdateSourceTrigger = UpdateSourceTrigger;
+				_binding.Mode = BindingMode.TwoWay;
+
+				var designItem = surface.DesignContext.Services.Component.GetDesignItem(ctx);
+
+				_converter = new DesignItemSetConverter(designItem, _propertyName, SingleItemProperty);
+				_binding.Converter = _converter;
+
+				_targetObject.SetBinding(_targetProperty, _binding);
+			}
+			else
+			{
+				_targetObject.ClearValue(_targetProperty);
+			}
+		}
+
+		private class DesignItemSetConverter : IValueConverter
+		{
+			private DesignItem _designItem;
+			private string _property;
+			private bool _singleItemProperty;
+
+			public DesignItemSetConverter(DesignItem desigItem, string property, bool singleItemProperty)
+			{
+				this._designItem = desigItem;
+				this._property = property;
+				this._singleItemProperty = singleItemProperty;
+			}
+
+			public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+			{
+				return value;
+			}
+
+			public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+			{
+				var changeGroup = _designItem.OpenGroup("Property: " + _property);
+
+				try
+				{
+					var property = _designItem.Properties.GetProperty(_property);
+
+					property.SetValue(value);
+
+
+					if (!_singleItemProperty && _designItem.Services.Selection.SelectedItems.Count > 1)
+					{
+						var msg = MessageBox.Show("Apply changes to all selected Items","", MessageBoxButton.YesNo);
+						if (msg == MessageBoxResult.Yes)
+						{
+							foreach (var item in _designItem.Services.Selection.SelectedItems)
+							{
+								try
+								{
+									property = item.Properties.GetProperty(_property);
+								}
+								catch(Exception)
+								{ }
+								if (property != null)
+									property.SetValue(value);
+							}
+						}
+					}
+
+					changeGroup.Commit();
+				}
+				catch (Exception)
+				{
+					changeGroup.Abort();
+				}
+
+				return value;
+			}
+		}
+	}
+}