Fixes the following in RegisterXamlComponentRecursive method (called for example on Paste):

- Getting the correct namescope for RootItem (the INameScope case was not checked).

- Clears the local namescope for the object if it exists, otherwise name changes will be registered in the local namespace instead of RootItem document namespace.

- Only adds _Copy (or CopyX, where X is an integer) if the previous name did not already end with _Copy. This prevents names as "myname_Copy_Copy_Copy..." to occur when copying and pasting already copied elements.

- Registers the new name to the RootItem namescope, only setting site.Name is not enough as its not yet a part of the RootItem document namescope.

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/Xaml/XamlComponentService.cs

@@ -90,24 +90,37 @@ namespace ICSharpCode.WpfDesign.Designer.Xaml
 			}
 			
 			if (_context.RootItem != null && !string.IsNullOrEmpty(site.Name)) {
-				var nameScope = _context.RootItem.Component as INameScope;
-				nameScope = NameScope.GetNameScope((DependencyObject) _context.RootItem.Component);
-				var fnd = nameScope.FindName(site.Name);
-				
-				if (fnd != null) {
-					string newNm = site.Name + "_Copy";
-					fnd = nameScope.FindName(newNm);
-					if (fnd == null)
-						site.Name = newNm;
-					else {
+				var nameScope = NameScopeHelper.GetNameScopeFromObject(_context.RootItem.Component);
+
+				if (nameScope != null) {
+					// The object will be a part of the RootItem namescope, remove local namescope if set
+					NameScopeHelper.ClearNameScopeProperty(obj.Instance);
+					
+					string newName = site.Name;
+					if (nameScope.FindName(newName) != null) {
+						int copyIndex = newName.LastIndexOf("_Copy", StringComparison.Ordinal);
+						if (copyIndex < 0) {
+							newName += "_Copy";
+						}
+						else if (!newName.EndsWith("_Copy", StringComparison.Ordinal)) {
+							string copyEnd = newName.Substring(copyIndex + "_Copy".Length);
+							int copyEndValue;
+							if (Int32.TryParse(copyEnd, out copyEndValue))
+								newName = newName.Remove(copyIndex + "_Copy".Length);
+							else
+								newName += "_Copy";
+						}
+						
 						int i = 1;
-						while (fnd != null) {
-							newNm = site.Name + "_Copy" + i;
-							fnd = nameScope.FindName(newNm);
-							i++;
+						string newNameTemplate = newName;
+						while (nameScope.FindName(newName) != null) {
+							newName = newNameTemplate + i++;
 						}
-						site.Name = newNm;
+						
+						site.Name = newName;
 					}
+
+					nameScope.RegisterName(newName, obj.Instance);
 				}
 			}
 			return site;

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

@@ -10,7 +10,7 @@ namespace ICSharpCode.WpfDesign.XamlDom
 	/// <summary>
 	/// Static methods to help with <see cref="System.Windows.Markup.INameScope"/> operations on Xaml elements.
 	/// </summary>
-	internal static class NameScopeHelper
+	public static class NameScopeHelper
 	{
 		/// <summary>
 		/// Finds the XAML namescope for the specified object and uses it to unregister the old name and then register the new name.
@@ -18,16 +18,11 @@ namespace ICSharpCode.WpfDesign.XamlDom
 		/// <param name="namedObject">The object where the name was changed.</param>
 		/// <param name="oldName">The old name.</param>
 		/// <param name="newName">The new name.</param>
-		public static void NameChanged(XamlObject namedObject, string oldName, string newName)
+		internal static void NameChanged(XamlObject namedObject, string oldName, string newName)
 		{
 			var obj = namedObject;
 			while (obj != null) {
-				var nameScope = obj.Instance as INameScope;
-				if (nameScope == null) {
-					var depObj = obj.Instance as DependencyObject;
-					if (depObj != null)
-						nameScope = NameScope.GetNameScope(depObj);
-				}
+				var nameScope = GetNameScopeFromObject(obj.Instance);
 				if (nameScope != null) {
 					if (oldName != null) {
 						try {
@@ -52,5 +47,33 @@ namespace ICSharpCode.WpfDesign.XamlDom
 				obj = obj.ParentObject;
 			}
 		}
+		
+		/// <summary>
+		/// Gets the XAML namescope for the specified object.
+		/// </summary>
+		/// <param name="obj">The object to get the XAML namescope for.</param>
+		/// <returns>A XAML namescope, as an <see cref="INameScope"/> instance.</returns>
+		public static INameScope GetNameScopeFromObject(object obj)
+		{
+			var nameScope = obj as INameScope;
+			if (nameScope == null) {
+				var depObj = obj as DependencyObject;
+				if (depObj != null)
+					nameScope = NameScope.GetNameScope(depObj);
+			}
+			
+			return nameScope;
+		}
+		
+		/// <summary>
+		/// Clears the <see cref="NameScope.NameScopeProperty"/> if the object is a <see cref="DependencyObject"/>.
+		/// </summary>
+		/// <param name="obj">The object to clear the <see cref="NameScope.NameScopeProperty"/> on.</param>
+		public static void ClearNameScopeProperty(object obj)
+		{
+			var depObj = obj as DependencyObject;
+			if (depObj != null)
+				depObj.ClearValue(NameScope.NameScopeProperty);
+		}
 	}
 }