Vs2008 XAML Visual Designer Exception when using a custom template (Alloy copy)

NB : New thread so as not to pollute the other which I see has already been referenced from a sticky :)

Following on from my previous post, I have an oddity.  The custom style compiles and runs without error, but displays an exception when displayed in the vs2008 visual designer.

if the custom style is the default style applied to the grid as it's default, i get:

Cannot add element to 'Columns'; the property value is null.  Error at object 'System.Windows.Controls.GridViewColumn', Line 1 Position 643.
   at System.Windows.Markup.XamlParseException.ThrowException(String message, Exception innerException, Int32 lineNumber, Int32 linePosition, Uri baseUri, XamlObjectIds currentXamlObjectIds, XamlObjectIds contextXamlObjectIds, Type objectType)
   at System.Windows.Markup.XamlParseException.ThrowException(ParserContext parserContext, Int32 lineNumber, Int32 linePosition, String message, Exception innerException)
   at System.Windows.Markup.BamlRecordReader.ThrowExceptionWithLine(String message, Exception innerException)
   at System.Windows.Markup.BamlRecordReader.ThrowException(String id, String parameter)
   at System.Windows.Markup.BamlRecordReader.InitPropertyCollection(BamlCollectionHolder holder, ReaderContextStackData context)
   at System.Windows.Markup.BamlRecordReader.GetCollectionHolderFromContext(ReaderContextStackData context, Boolean toInsert)
   at System.Windows.Markup.BamlRecordReader.GetListFromContext(ReaderContextStackData context)
   at System.Windows.Markup.BamlRecordReader.SetPropertyValueToParent(Boolean fromStartTag, Boolean& isMarkupExtension)
   at System.Windows.Markup.BamlRecordReader.ReadElementEndRecord(Boolean fromNestedBamlRecordReader)
   at System.Windows.Markup.BamlRecordReader.ReadRecord(BamlRecord bamlRecord)
   at System.Windows.StyleHelper.LoadOptimizedTemplateContent(DependencyObject container, ParserContext parserContext, OptimizedTemplateContent optimizedTemplateContent, FrameworkTemplate frameworkTemplate, IComponentConnector componentConnector, IStyleConnector styleConnector, List`1 affectedChildren, UncommonField`1 templatedNonFeChildrenField)
   at System.Windows.FrameworkTemplate.LoadContent(DependencyObject container, List`1 affectedChildren, UncommonField`1 templatedNonFeChildrenField)
   at System.Windows.StyleHelper.ApplyTemplateContent(UncommonField`1 dataField, DependencyObject container, FrameworkElementFactory templateRoot, Int32 lastChildIndex, HybridDictionary childIndexFromChildID, FrameworkTemplate frameworkTemplate)

(etc...)

If the custom style resource dictionary is loaded, but not actually referenced, I get:

Object reference not set to an instance of an object.
   at Mindscape.WpfPropertyGrid.ManyToNodeConverter.Convert(Object value, Type targetType, Object parameter, CultureInfo culture)
   at System.Windows.Data.BindingExpression.TransferValue(Object newValue, Boolean isASubPropertyChange)
   at System.Windows.Data.BindingExpression.Activate(Object item)
   at System.Windows.Data.BindingExpression.AttachToContext(AttachAttempt attempt)
   at System.Windows.Data.BindingExpression.MS.Internal.Data.IDataBindEngineClient.AttachToContext(Boolean lastChance)
   at MS.Internal.Data.DataBindEngine.Task.Run(Boolean lastChance)
   at MS.Internal.Data.DataBindEngine.Run(Object arg)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Boolean isSingleParameter)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Boolean isSingleParameter, Delegate catchHandler)

Happy to provide the modified samples solution on request (however I've *basically* just followed the steps linked above).

Any clues?

I've committed a fix that appears to fix the first exception.  It will be included in the 20 June nightly build, available from about 1430 GMT.  One limitation is that you will not see captions for design-time sample data items in the visual designer.  This is a known issue but it's a fairly low priority I'm afraid.

The second exception (if you don't reference the custom style resource dictionary) may be fixed in the nightly build -- looking at the code it should no longer be possible for that exception to be thrown from that part of the code -- but I don't think this is a critical scenario for you, right?  If it is important and the nightly doesn't fix it, let us know and we'll investigate.

You're right, niether of these are critical issues since our application still compiles and runs just fine :)

Thanks for the quick turnaround - I'll check out the nightly once it's up.