Fixed so nodes in the property grid gets DesignItemProperty instances that really represents attached properties when an attached property is used.

When setting a property value as attribute, fixed so namespace prefix is only used for attached properties, and if no prefix is defined for a non-default namespace a new unique prefix is generated.

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/PropertyGrid/PropertyGrid.cs

@@ -226,7 +226,7 @@ namespace ICSharpCode.WpfDesign.Designer.PropertyGrid
 
 		void AddNode(MemberDescriptor md)
 		{
-			var designProperties = SelectedItems.Select(item => item.Properties[md.Name]).ToArray();
+			var designProperties = SelectedItems.Select(item => item.Properties.GetProperty(md)).ToArray();
 			if (!Metadata.IsBrowsable(designProperties[0])) return;
 
 			PropertyNode node;
@@ -252,7 +252,7 @@ namespace ICSharpCode.WpfDesign.Designer.PropertyGrid
 		Category PickCategory(PropertyNode node)
 		{
 			if (Metadata.IsPopularProperty(node.FirstProperty)) return popularCategory;
-			if (node.FirstProperty.Name.Contains(".")) return attachedCategory;
+			if (node.FirstProperty.IsAttachedDependencyProperty()) return attachedCategory;
 			var typeName = node.FirstProperty.DeclaringType.FullName;
 			if (typeName.StartsWith("System.Windows.") || typeName.StartsWith("ICSharpCode.WpfDesign.Designer.Controls."))
 				return otherCategory;

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.XamlDom/Project/XamlProperty.cs

@@ -327,21 +327,34 @@ namespace ICSharpCode.WpfDesign.XamlDom
 
 		internal XmlAttribute SetAttribute(string value)
 		{
-			string ns = ParentObject.OwnerDocument.GetNamespaceFor(PropertyTargetType);
 			string name;
+			var element = ParentObject.XmlElement;
+
 			if (IsAttached)
+			{
 				name = PropertyTargetType.Name + "." + PropertyName;
+
+				string ns = ParentObject.OwnerDocument.GetNamespaceFor(PropertyTargetType);
+                string prefix = element.GetPrefixOfNamespace(ns);
+
+                if (String.IsNullOrEmpty(prefix))
+                {
+                    prefix = ParentObject.OwnerDocument.GetPrefixForNamespace(ns);
+                }
+
+                if (!string.IsNullOrEmpty(prefix))
+				{
+					element.SetAttribute(name, ns, value);
+					return element.GetAttributeNode(name, ns);
+				}
+			}
 			else
+			{
 				name = PropertyName;
-
-			var element = ParentObject.XmlElement;
-			if (string.IsNullOrEmpty(element.GetPrefixOfNamespace(ns))) {
-				element.SetAttribute(name, value);
-				return element.GetAttributeNode(name);
-			} else {
-				element.SetAttribute(name, ns, value);
-				return element.GetAttributeNode(name, ns);
 			}
+
+			element.SetAttribute(name, value);
+			return element.GetAttributeNode(name);
 		}
 
 		internal string GetNameForMarkupExtension()

src/AddIns/DisplayBindings/WpfDesign/WpfDesign/Project/ExtensionMethods.cs

@@ -2,6 +2,7 @@
 // This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
 
 using System;
+using System.ComponentModel;
 using System.Windows;
 
 namespace ICSharpCode.WpfDesign
@@ -23,5 +24,51 @@ namespace ICSharpCode.WpfDesign
 				Math.Round(rect.Height, PlacementInformation.BoundsPrecision)
 			);
 		}
+
+		/// <summary>
+		/// Gets the design item property for the specified member descriptor.
+		/// </summary>
+		public static DesignItemProperty GetProperty(this DesignItemPropertyCollection properties, MemberDescriptor md)
+		{
+			DesignItemProperty prop = null;
+
+			var pd = md as PropertyDescriptor;
+			if (pd != null)
+			{
+				var dpd = DependencyPropertyDescriptor.FromProperty(pd);
+				if (dpd != null)
+				{
+					if (dpd.IsAttached)
+					{
+						prop = properties.GetAttachedProperty(dpd.DependencyProperty);
+					}
+					else
+					{
+						prop = properties.GetProperty(dpd.DependencyProperty);
+					}
+				}
+			}
+
+			if (prop == null)
+			{
+				prop = properties[md.Name];
+			}
+
+			return prop;
+		}
+		
+		/// <summary>
+		/// Gets if the specified design item property represents an attached dependency property.
+		/// </summary>
+		public static bool IsAttachedDependencyProperty(this DesignItemProperty property)
+		{
+			if (property.DependencyProperty != null)
+			{
+				var dpd = DependencyPropertyDescriptor.FromProperty(property.DependencyProperty, property.DesignItem.ComponentType);
+				return dpd.IsAttached;
+			}
+
+			return false;
+		}
 	}
 }

src/AddIns/DisplayBindings/WpfDesign/WpfDesign/Project/PropertyGrid/PropertyNode.cs

@@ -34,7 +34,24 @@ namespace ICSharpCode.WpfDesign.PropertyGrid
 		/// <summary>
 		/// Gets the name of the property.
 		/// </summary>
-		public string Name { get { return FirstProperty.Name; } }
+		public string Name
+		{
+			get
+			{
+				var dp = FirstProperty.DependencyProperty;
+				if (dp != null)
+				{
+					var dpd = DependencyPropertyDescriptor.FromProperty(dp, FirstProperty.DesignItem.ComponentType);
+					if (dpd.IsAttached)
+					{
+						// Will return the attached property name in the form of <DeclaringType>.<PropertyName>
+						return dpd.Name;
+					}
+				}
+
+				return FirstProperty.Name;
+			}
+		}
 		
 		/// <summary>
 		/// Gets if this property node represents an event.
@@ -366,7 +383,7 @@ namespace ICSharpCode.WpfDesign.PropertyGrid
 				if (ValueItem != null) {
 					var list = TypeHelper.GetAvailableProperties(ValueItem.Component)
 						.OrderBy(d => d.Name)
-						.Select(d => new PropertyNode(new[] { ValueItem.Properties[d.Name] }, this));
+						.Select(d => new PropertyNode(new[] { ValueItem.Properties.GetProperty(d) }, this));
 
 					foreach (var node in list) {
 						if (Metadata.IsBrowsable(node.FirstProperty)) {